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NOTES 


ON 


MECHANICAL DRAWING 


PREPARED FOR THE USE OF 
STUDENTS IN 


ELEMENTARY AND ADVANCED 
MECHANICAL DRAWING 


BY 

HORACE P. FRY, B. S. In E. E. 

ASST. PROF. OF MECHANICAL DRAWING 
DEPARTMENT OF MECHANICAL ENGINEERING 
THE TOWNE SCIENTIFIC SCHOOL 
UNIVERSITY OF PENNSYLVANIA 

MEMBER OF THE SOCIETY FOR THE 
PROMOTION OF ENGINEERING EDUCATION. 


11LADELPHI 

1919 




COPYRIGHT, 1919, 
BY 

HORACE P. FRY 


SIXTH EDITION. 





© Cl. A 512965 

APR -7 1919 

- ytyO r / / 



PREFACE. 


Mechanical drawings are required in all constructive work 
and, as the name implies, are made with precision instruments. 
In making such drawings, strict adherence to the principles of 
projection, accuracy and neatness in execution remove all doubts 
as to what is intended and make a drawing perfectly clear to all 
accustomed to reading and working from them. 

The student should realize that the user of a drawing con¬ 
structs as the drawing shows, not as the one who made the drawing 
intended to show. 

The matter contained in these Notes is not an exhaustive 
treatise on mechanical drawing, but is intended to supplement 
class instruction. 

These Notes contain recognized standards, conventions and 
technic used in American practice, together with tables and other 
information valuable in drawing. 

Questions are continually arising in a student’s mind as to 
just how to represent certain conditions, and since he will remember 
longer that which he looks up for himself, it is his duty to answer 
these questions by referring to the standards, conventions and 
technic of practice before questioning his instructor. 

The previous editions of the Notes were developed along 
lines suggested by students’ questions. 

The present edition has been enlarged along the same lines. 
Part of the subject-matter has been rewritten to increase its scope. 

The numbering of the paragraphs under each topic provides 
a ready reference for the student’s attention relative to errors in 
his work and for study or other assignment. 

The topic headings and the more important features under 
each have been emphasized by bold-face type. 

The lack of complete uniformity in all lines of work using 
mechanical drawings makes it impossible to include in these Notes 
anything except fundamentals. 

Philadelphia, Pa., Horace P. Fry. 

September, 1916. 

PREFACE TO SIXTH EDITION. 

The present edition is practically the same as the previous 
one. A few paragraphs have been rewritten. 

A Checking Index has been found most useful in correcting 
student’s work, it has been added directly after the regular index. 

January, 1919. H. P. F. 


(3) 




CLASSIFICATION OF DRAWINGS. 


1. DRAWINGS are divided into two classes—those made 
purely freehand and those made with instruments of precision. 

2. FREEHAND DRAWINGS are made for artistic effects, 
historical records or the purpose of registering mental pictures. 
They show only that which is visible and are readily understood. 

3. FREEHAND SKETCHES for constructive purposes are 
made with few or no instruments, but in other respects they are 
the same as a mechanical drawing. 

4. MECHANICAL DRAWINGS are made with instruments 
of precision to convey, from one person to another, complete and 
accurate information of the visible and invisible structure of an 
object, not necessarily of a mechanical nature. They are made 
according to definite principles of projection and are fully under¬ 
stood only by those who have been trained in this so-called ‘ * graphic 
language.” 

5. GEOMETRICAL DRAWINGS are made with instruments 
and involve the principles of Geometry in solving problems. A 
knowledge of these principles is valuable and fundamental, but 
very few of them are used, since anyone making a Mechanical 
Drawing has at his command instruments for obtaining the same 
results by quicker means. For example, drawing lines parallel, 
erecting perpendiculars and drawing arcs (fillets) tangent to lines. 

ESSENTIALS. 1. A designer, in any line of work, uses draw¬ 
ing as the means of expressing his ideas. 

2. The aim in learning how to draw is to acquire the ability 

to express ideas graphically, so they may be put into concrete 
form for practical use. 

3. In making a mechanical drawing the draftsman (meaning 
anyone making the drawing) should remember that correctness in 
projection, accuracy, practical dimensioning, clearness, neatness, 
necessary notes and a proper title are all essential to the working 
value of the drawing, since the object of such a drawing is to enable 
one to make that which has been pictured without recourse to any 
other information than that contained on the drawing. The 
artisan constructs as the drawing shows, not as the draftsman may 
have intended to show. 


(4) 



INSTRUMENT LIST. 


1. THE MATERIALS SPECIFIED are standard and repre¬ 
sentative types used in good practice. A novice should consult 
his instructor before making any substitutions until he learns 
that the best are cheapest in the end. 

2. THE COMPLETE EQUIPMENT should be at hand at 
all times, and contain the following items: [all consumed, broken 
and lost portions to be replaced at once]. 

A. One set of approved Drawing Instruments in a morocco-covered 
case having two metal hinges and clasps (see Fig. 1), the set 
to include 

5§" compass, pen, pencil and lengthening bar, fixed 
needle point leg. 

3J" bow spacer. 

3J" bow pencil with needle point. 

3J" bow pen with needle point. 

5" ruling pen. 

Nickel-plated lead case. 

[Set No. 2050, made by Theodore Altender & Sons, 
Philadelphia.] 



Fig. i. 

B. Triangular box-wood scale having the following scales thereon: 

12", 9", 6", 4", 3", 2", 1§" to the foot, and 50 parts to the 
inch divided the full length of the scale. 

C. One 8"—45° celluloid triangle. Not less than rg-" thick. 

D. One 12"—60° celluloid triangle. Not less than thick. 

(5) 










6 


E. 

F. 

G. 

H. 

I. 

J. 

K. 

L. 

M. 

N. 

O. 

P. 


Q. 



Fig. 2. 


T-square, 30" blade (not set in head). Blade to have celluloid 
edges tongued and grooved to wood. 

One celluloid irregular curve, as shown 
in Fig. 2. (K. and E. No. 19.) 

One Linograph (senior size) may be sub¬ 
stituted for C. D. and F. 

Two 6H and one H drawing pencils. 

(Kooh-i-noor, Eldorado or Castell.) 

One bottle of black waterproof drawing ink. Higgins’. 

One erasing shield. Polished on one side only. 

One small ink eraser. (E. Faber’s improved.) 

One large pencil eraser. (E. Faber’s ruby or emerald.) 

One art gum cleaning rubber (large). 

One dozen §" thumb tacks. (Thin head, K. & E. Ideal.) 

Two sheets 22" x 30" drawing paper. (K. & E. Normal.) 

Drawing board, white pine, 23" x 31" with cleats on the back; 
face of board must not be shellacked. Each cleat to have a 
3" x r 3 g" slot cut through next to board. Slots must be 
in line and about central of the cleats. 

One drawing kit containing paper wallet, freehand lettering 
paper, pencil file, Eagle 1928 penholder, 390 Gillott pens and 
516F Leonard’s ball pointed pens, ink-rag, Dennison paper 
clips and 4" x 6" scratch pad. 


1. USE OF INSTRUMENTS. Every article itemized in the 
foregoing list is required and used for a specific purpose. 

2. The uses of the instruments and ways of handling them 

are best explained by demonstrations and proficiency acquired 
by constant practice. 

3. Triangles are used to obtain angles of 15°, 75° and any 
multitude of 15° as shown in Fig. 3. 



Fig. 3. 
















7 


4. Chisel points must be used on all instrument leads and 
pencils. Cut the wood back for 1J", exposing the lead for f", 
then flatten the lead by rubbing opposite sides on a file and bring 
to a knife edge by using a slight rocking motion. This point will 
have the appearance of the ruling pen point, but broader. 

1. A NUMBER CIRCLE is placed in the lower left corner of 
each drawing and tracing. Its size, form and location are shown 
in Fig. 4. 

2. The classification number of the drawing is to be placed 
in the central zone of the number circle. 



3. The course number is to be placed in the top segment 
of the number circle and the class section number in the bottom one. 

4. A drawing showing more than one part, each having an 
individual part number, must have the part numbers in separate 
circles. 

5. The part number circle is placed near the principle view 
of the part and connected to the view by a leader as shown in 
Fig. 5. 

6. Pattern numbers are serial numbers entered thus: Patt. 
8765 on the principle view in a conspicuous place. See Fig. 5. 






























































8 


7. Tracing index number is a serial number assigned, for 
designating and filing purposes, from an index when a tracing is 
completed. Block letters and numbers §" high as shown in Fig. 40 
are suitable for this purpose. The letter designating the size of 
sheet and the serial number are placed on the lower right margin 
as shown in Fig. 8. 

SIZE OF SHEETS. 1. Drawings are made on sheets, ruled 
and cut to standard forms. Use the forms shown in Figs. 6, 7 
and 8, as specified for each type of work. 

2. Form 1-E signifies a sheet cut exactly 10" x 14" and ruled 
with a margin. 

3. Sheets are to be trimmed to size after the drawing has 
been completed. (See reference on trimming.) 

SIZE OF TRACINGS. 1. Tracings are to be ruled and 
trimmed to one of the sizes shown in Fig. 8 unless specific orders 
to the contrary are given. 

2. A tracing is trimmed to size after it has been checked 
and all corrections have been made. (See reference on trimming.) 


FORM 

SHEET 

SIZE 

w 

L. 

1 

A 

ad 

28' 

e> 

\4 j 

ad 

e: 

7c? 

w 


© 


Fig. 6. 
























9 


*-rao '— - 

“T PLACE TITLE HERE 

ON FORM 2 

SEE LETTERING andTitlES 


FORM 


SHEET 

SIZE 

w 

L- 


2d 



\4 

zd 

EL 

\d 

1 4 ' 


PLACE TITLE HERE 

ON FORM 3 

* L SEE LETTERlN6Ar4D TITLE! S 


Fig. 7. 



Fig. 8. 
















































10 


TRIMMING. 1. Trim drawing paper with a sharp penknife, 
using the lower edge of your T-square as a guide and the back 
of your drawing-board to cut on. Never use the face of board 
or table top. Trim drawings when completed. 

2. Trim tracing cloth with shears, leaving J" outside of margin 
all around for thumb-tacks, trim tracings to size after they have 
been checked and corrections made. 

3. Drawing and tracing sheets are to be neatly trimmed to 
exact size of form specified and have no thumb-tack holes in them. 

PROJECTION. 1. Perspective projection gives on one 
plane in one view an image of the object as the eye sees it. The 
image is formed on the plane of projection at the intersection with 
it of projection lines drawn from a point (the eye) to all points 
of the object. This method finds its greatest use in Architecture. 

2. Axonimetric projection gives on one plane one view of an 
object that shows its three dimensional surfaces, length, height 
and width. The method is used to obtain pictorial effect, the 
illustration in Fig. 10 having been drawn by this method. 

3. Isometric projection, a particular type of axonimetric 
projection, is used as a ready means of making a Mechanical or 
Freehand Isometric Drawing of an object. This method was 
used in drawing the illustration for Fig. 9. (See reference on 
Isometric Drawing.) 

4. Orthographic projection gives on one plane as many views 
of an object as may be desired by revolving into that plane all 
planes of projection. A projection (view) on a plane of projection 
is formed on the plane at the intersection with it of parallel lines 
drawn perpendicular to the plane from all points of the object. 
See projection on horizontal plane in Fig. 10. (Read para¬ 
graph 11.) 

5. Coordinate planes of projection are two planes, one 
vertical and one horizontal, intersecting at right angles and form¬ 
ing four dihedral angles known as first, second, third and fourth 
angle, as indicated in Fig. 9. 

6. A profile plane of projection is one at right angles to the 
two coordinate planes; it is shown in Fig. 9. 

7. Auxiliary planes of projection are planes other than the 
coordinate and profile planes and when used they must be passed 
at right angles to a previous plane of projection. 

8. All planes of projection are considered indefinite in extent. 
An object may be placed anywhere in any one of the four angles 
and projected upon the planes. 


11 


9. Third angle projection gives the most logical and practical 
views; it is used universally in American practice and all drawings 
are to be made accordingly unless otherwise directed. 

10. In third angle projection the planes of projection are 
between the observer and the object. Let it be assumed, as in 
Fig. 10, that the object is surrounded by transparent planes of 
projection and the object to be projected on all of the planes by 
drawing projection lines as shown on the horizontal plane. 



11. Projection lines are lines drawn perpendicular from 
points of the object to the planes of projection. 

12. The trace of a line is a point where the line, prolonged 
if necessary, cuts a plane. 

13. The trace of a plane is a line where the plane, extended 
if necessary, cuts another plane. 

14. The true length of a line or the true size and shape of 
a plane surface will be the projection of the line or surface on a 
plane parallel to the line or surface. 

15. A Descriptive Geometry should be consulted for a com¬ 
plete treatment of the subject. 








12 



POINTS 


TRACES 


PLAN OR 
LJ TOP VIEW 


LEFT SIDE VIEW 


FRONT VIEW 


RI6HT SIDE VIEW 




OR ELEVA 


TIONS 


BACK VIEW 



_ BOTTOM 
VIEW 


THE VIEWS MARKED THUS X 
ARE THE ONES MOST USED 
IN PRACTICE. THE OTHER 
VIEWS AND THOSE ON 
OBLIQUE FLAMES ARE USED 
WHEN CONDITIONS REQUIRE 
THEM. 


Fig. ll. 
























































13 


ARRANGEMENT OF VIEWS. 1 . Let one of the planes, 
AB C D, in Fig. 10, coincide with the plane of the paper and revolve 
each of the others about its intersection with that plane and toward 
the observer, until they are all in the plane of the paper, then the 
views will be in their proper relative positions. 

2. The names and positions of the views when properly pro¬ 
jected and revolved are shown in Fig. 11. 

SCALES. 1. Full -size drawings of objects are not always 
possible or practical, and in such cases they must be made one-half 
size or some other conventional size. A scale is used to make a 
drawing less than full size. 

2. A scale is a fraction of the unit measure, one foot in U. S. 
practice, subdivided into the same number of parts that the unit 
is divided and is used in the same way as the full-size unit. 

3. The standard scales used in Machine Drawing are 9", 
6", 4", 3", 2", 1|" and 1" to the foot. Drawings should be made 
to one of these scales or full size (never larger). 

4. Scales 3", 1§", J", i", f", i", A", A" and J" to the foot 
are used by Architects. Scales 10, 20, 30, 40, 50, and 100 feet to 
an inch are used in Civil Engineering work. 

5. The words size and scale should not occur together. 
Either Half size or Scale 6" = T is correct. Scale half size is 
incorrect. Scale 9" to 1' is A, or J size. Scale 3" to 1' is A, or 
i size. 

6. To determine the scale for a drawing assume rectangles, 
as in Fig. 12, to represent the least areas which will contain the 
different views desired. The dimensions of the rectangles being 
the over-all dimensions of the object to be drawn. If A+B is less 
than Li, the length of the paper, the drawing can be made full 
size, provided C+D<Wi. If the paper is not large enough, 
multiply the dimensions (Li and Wi) of the paper by 12 divided 
by a scale; that is, either i, 2, 3, 4, 6 or 8, until the paper is 
increased enough to draw the object full size; the reciprocal of 
the multiplier will be the size the object can be drawn on the 
original paper size Li+Wi. If, for example, a sheet should have 
to be made four times longer in order to draw the object full size, 
the object can be drawn J size, or scale 3" to V on the original sheet. 

7. Decide which views are required to properly and clearly 
show the object, before starting the drawing, and lay out the 
sheet so that the views, when properly placed, will leave room for 
the title also a bill of material when required. Move the views 
from the center of the paper rather than reduce the scale. 


14 


LAYING OUT VIEWS. 1. The distance between views 
should not be less than or more than 1^" (F and J, Fig. 12), 

depending on the space required for dimensions. 

Thfe rectangles previously referred to in Fig. 12 are not to be 
used in the actual laying out of the views. 

2. The distance between views and margins is determined 
graphically as follows: Lay off from the left margin a distance, 
to the scale that will be used, equal to the over-all lengths (A+B, 
Fig. 12), of the views and add on the full size distance allowed 
between views and measure to full size the remaining distance 



Fig. 12. 


to the right-hand margin. This remainder is divided equally 
between the two sides (H and K), but is not figured closely. 

3. To lay out a drawing the important center line or base 
line in each view is carefully located and from these the drawing 

is accurately constructed. 

Begin at the left and (see Fig. 12) mark off the full-size 
distance (H) that the view will be from the left margin; add to 
this the scale distance to the center line, and so on to the successive 
center lines. The horizontal center lines are located by measuring 
from the top margin. 












































































15 


4. Accuracy in laying out a drawing is necessary, since the 
operation of drawing is that of building up on paper the views 
of an object, which in most cases does not exist; in other words, 
it is designing (building) by steps, and inaccuracies in the building 
are not permissible. 

5. Draw the views simultaneously. There is no gain in 
completing one at a time. Observe the principles of projection 
and the practice of reading drawings from the bottom and the 
right margins of the sheet. 

6. The base of an object as drawn should face the bottom 
or right margin to avoid having the object appear inverted. 

VISIBLE! OR FULL LINE. 

LIGHT LINE!, RATIO ITQ3 ; 5HAOE LINE . 

invisible: or dotted lines. 

Break Joirsi-ra when Libels are Adjacent 


CENTER LINE!. 


DIMENSION LINE!. 


CONSTRUCTION LINE. 


IRREGULAR LINE:. 


Fig. 13. 

LINES. 1 . All drawings are to be made with a 6H sharp 
chisel-pointed pencil. (See Par. 4, page 7.) The pencil work is to 
be clear and distinct and have a finished appearance before any 
inking is done. It is not necessary to pencil cross-hatching or 
dimensions on a drawing that is to be inked. Cross-hatching may 
be done lightly freehand to indicate the areas to be sectioned. 

2. Full lines are drawn for all visible edges. (See Fig. 13 for 
width of line.) 

3. Dotted lines are used to show hidden 
edges, and should be drawn as the clearness of the 
drawing is thereby furthered. Dotted lines are 
in reality short dashes with spaces about J the 
length of the dash. (See Fig. 13.). The first and 
last dash of a dotted line should touch the lines 
at which the hidden edge actually terminates. 
(See Fig. 14.) 


THUS 


NOT 


Fig. 14. 




















16 


4. Parallel dotted lines that lie close together, should have the 
dashes and spaces staggered as shown in Fig. 13. The eye can more 
readily follow broken lines with spaces staggered. 

5. The full lines in the two views, Fig. 15, represent lines in 
full view, and the dotted lines hidden ones. If the drawing is too 
much complicated by showing all the hidden edges, some may be 
omitted, provided the clearness of the drawing is not impaired. 



6. Center lines are long dash and dot black lines somewhat 
lighter than the outline. (See Fig. 13.) They are drawn through 
all axes of symmetry, the centers of all holes, bolts and rivets and 
where dimensions are to be given from some fixed line. The breaks 
on each side of the dots should be short and should be in open 
spaces, not where lines are crossed. (See Fig. 15.) 

7. Center lines may be drawn continuous between different 
views of the same object; they must be offset for clearness when 
views of different objects are adjacent. (See Figs. 15 and 16.) 

8. Irregular lines are used to denote a break when a portion 
of a view is shown in section. (See Figs. 13 and 16.) 





























17 



VS 





CD 





Section onA-B 






















































































18 


9. Construction lines are fine dash lines (see Fig. 13). They 
are used largely in elementary work to connect the projections 
on two adjacent planes. These lines should not touch the points 
between which they are drawn. (See Figs. 9 and 10.) 



Fig. 17. 


10. Adjacent part lines are drawn like construction lines. 

They are used to show a part that is adjacent to the piece drawn. 

11. Extension or reference lines are full light lines used to pro¬ 
long the lines of a drawing in order to place a dimension away from 
the view or at a more readable place; they should not quite touch 
the view so that they may not be taken for part of it. (See Figs. 
15 and 16.) 


























19 


SHADE LINES. 1. Shade lines are heavy black lines about 
three times as wide as the outline. (See Fig. 13.) They are 
drawn to distinguish readily the raised and depressed portions of 
an object and make the views stand out. (See Fig. 15.) The light 
is supposed to fall on all views of the object from the upper left-hand 
comer of the drawing, in parallel rays, at an angle of 45° with the 
plane of the paper as shown by the arrows to the left in Fig. 17. 
No account is taken of the shadows cast by one portion of the 
object upon another. The position of shade lines is conventional; 
for example, in Fig. 15 the lower lines of the right-hand view do 
not, strictly speaking, represent the divisions between a light and 
a dark surface, yet it is the custom to shade them as shown. 

2. Draw all shade lines outside of the outlines. 

3. A line common to two surfaces is not shaded when both 
surfaces are visible. 

4. Shade the views independently of each other. By sliding 
a 45° triangle on the T-square and assuming the hypotenuse to be 
the ray of light, it is easy to determine, on just which surfaces the 
light does not impinge. (See Fig. 17.) 

5. Make all shade lines on a drawing of uniform width and 
equal to the widest part of a shaded arc. 

6. To shade a circle or arc always move the needle point of 
the instrument, without changing the radius, down to the right 
at an angle of 45° and a distance equal to the desired thickness of 
the shade line. Do this by eye. (See Fig. 17.) This will make 
the shade line blend into the outline at the proper place, i. e ., where 
the light ray is tangent to the curve. By placing the needle point 
in the original center and springing the pen slightly outward, the 
space between the original and eccentric curve can be filled in 
easily. 

7. To shade an arc that joins a shade line at each end, change 
the radius without moving the needle from the original center, 
draw a concentric arc and fill in the intervening space. 

8. Pencil lines are not shaded. 

9. Shade lines are not used on tracings. All lines are heavy. 

INKING IN. 1. Beginners make the mistake of drawing very 
fine ink lines that look neat but are not practical. If the nibs of 
the pen are forced close together the ink will not flow readily and 
the result is a fine gray line. A fairly heavy black line is correct 
(see Fig. 13); this may be obtained by opening the nibs of the pen 
so that the ink flows freely. 


20 


2. The outside of the pen must be kept free of ink. Never 
allow ink to harden in a pen; wipe frequently, and when through 
using see that the pen is quite clean. Do not scrape with a knife. 

3. When inking a drawing, first draw all circles and arcs, 
shading them as you go; after that draw the light straight lines, 
and finally the shaded straight lines. Dotted lines are not shaded. 

4. Lines, letters and figures must be black. If they have been 
lightened by erasure go over them until they are black. 

5. The surface of the paper that has been roughened by 
erasures can be restored by rubbing it with a piece of hard-surfaced 
paper, the finger nail, a piece of polished bone, ivory or celluloid. 
This will prevent the ink from spreading. 

6. Keep your paper and materials free from dust and particles 
of eraser to avoid blots and errors. Dust the drawing frequently. 


DIMENSIONING. 1. Dimension lines are full light lines 

drawn to connect the points between which a dimension is given. 
The lines are terminated by arrow heads, and the dimension is 


MAKE! F\ 6URES THUS I23-45GYS90 


4 


, I 


‘Ht 


6 ^Finished—A J 


56 4M 


Fig, 18. 


written in a break provided for that purpose, usually, but not 
necessarily, in the center of the line, as in Figs. 13 and 16. Dimen¬ 
sions should be kept in line. (See Fig. 15 at top and Fig. 18.) 

2. Arrow heads are made with a fine writing pen. They 

should be small, neat and sharp, and touch the line to which they 
refer. (See Figs. 18 and 19.) 

3. Dimension figures on a drawing should all be as near the 
same size as possible and not in proportion to the size of the 
dimension or drawing. Figures A" high, made as shown in Fig. 18, 
are large enough for all practical purposes. (See Fractions.) 

4. Figures printed in a line with lettering, as in a note or 

title, are made as high as the capital letters. 

5. Figures must be placed in open spaces, where they can be 
read distinctly, and not on top of lines. (See Fig. 19.) 

6. When the space is too small to contain a dimension, the 

arrow heads may be reversed and placed with the dimension 
outside the space as shown in Fig. 19, 












21 


7. For lack of room a dimension or note may be written in 
a convenient place and connected to the required point by a 
straight leader. Such a leader should always have an arrow head 
to indicate the point to which the dimension or note refers. (See 
Fig. 19.) 

8. Fractions must always have the dividing line at right angles 
to the figures, thus: §", never f i ", each figure in the numerator and 
denominator should, for clearness, be high the same as the whole 
number and should not touch the line. (See Fig. 18.) 

9. Inch and foot marks should be made neat and distinct 

(see sample under abbreviations) and accompany every dimension. 
(See Figs. 16 and 19.) 

10. Dimensions may be placed directly on the views but 

this frequently crowds the drawing too much. Dimensions should 



Fig. 19. 


be placed outside the views wherever clearness is gained thereby, 
using extension lines between which the dimensions are given. 

Dimension the views in blank before entering the dimension fig¬ 
ures; that is, first draw all extension lines and dimension lines, 
then make all arrow heads. Dimensions must be kept in line as 
shown at the top of Fig. 15 and in Figs. 18 and 19. 

11. Dimensions may be placed on a section but not on top 
of cross-hatching. Dimension a drawing before cross-hatching it. 

12. Dimension figures must always be placed at right angles 
to the dimension line and read only from the bottom or right- 
hand side of a drawing. (See Fig. 19.) 

13. Dimensions of machine parts are usually given in inches, 
thus: 2J", 27", the inch mark being placed after the figure. In 
large works, dimensions over two feet are given in feet and inches, 
thus: 4'—0", 20'—8|", 3'—0|". A dash between feet and inches 
and a zero for no inches are essential to avoid errors, 

















































22 


14. Necessary dimensions, for a piece and every feature of it, 
are length, width, thickness and location. They must be given on 
a drawing and care taken to avoid repetition. Give dimensions 
from finished surfaces wherever possible, from center lines, and 
from one center line to another. Center lines are not used as 
dimension lines. 

15. The size and location of holes must be given on the 
circular view. Locate holes from center lines or from center to 
center. Give cord distances and pitch circle diameter for holes 
on an arc; angular distances are undesirable. 

16. Give dimensions to full lines, in preference to dotted 

ones. 

17. Useful dimensions are those which are of most service to 
the user of the drawing who should never be required to do any 
calculating. A little thought as to the process the material must 
undergo in the construction of the object, will quickly determine 
what dimensions to give. 

18. Over-all dimensions are useful in getting out material 
and should be given where needed. 

19. Distribute the dimensions among all the views and do 
not crowd too many into one. Select dimensions that are the 
best for each view. 

20. A circular arc is dimensioned by a radial line, which need 
not extend to the center, with an arrow head only at the arc as 
shown for the fillet and round corner in Fig. 15. 

21. Circular pieces and bores are dimensioned by diameters, 

whether the complete circle or only a part of it is drawn; in the 
latter case Diam. must be printed after the dimension figure and 
the dimension line extended beyond the center as shown in the 
semicircular view, Fig. 38. 

22. Distances that are not to scale, as on a foreshortened view 
of a long piece, must have Not to Scale printed after the dimension 
figure. (See Fig. 19.) 

23. Omitted dimensions give trouble. To determine if a 
dimension is missing, scan for arrow heads the line in all views to 
which a dimension is desired. If no arrow head touches the line 
that dimension is missing. 

24. Tabulated dimensions are used for parts that are similar 
in shape but different in size. Only one of the parts is drawn and 
the dimensions of all parts tabulated as shown in Plate I. Dimen¬ 
sions that are common to all of the parts may remain on the 
views. 


23 


ABBREVIATIONS. The abbreviations and symbols most 
commonly used in practice are shown in Fig. 20. 


Angle L 

Center l/ne ± 

CENTER TO CENTER 

C/RCULAR R/TCH C. F 
C/RCUMEEREHCE C/rCUm. 

Degrees ° 

D/ametral f>/tch D. F 
D/ametef? D/arm. 
Feet Ft or ' 

F/n/sh mark $ 


Hexagonal Hex. 

Inches /ns. or " 
/ns/de /. S. 

Left hand L.H. 

Outs/de O. S. 

P/rCH C/RCl E DIAM. PCD- 
Ha d/us Fact, or F 

Fight hand F. H. 

Square 
7hreads 
%/reads fee inch TMsperh 


Sn. 

TnHs. 


Fig. 20. 


FINISH MARKS. Finish marks indicate that the surfaces 
marked must be machined to the exact dimension given, not 

necessarily polished. They are made with a writing pen (see 
Fig. 21) and should read from the bottom of the drawing only. 
(See Fig. 16.) The casting or forging is made full, where indicated 
by a finish mark, to allow for machining. When a piece is to be 
finished all over, omit these marks and print “finished” in the 
general title. (See Titles.) 



Fig. 21. 



























































24 


FINISHED SURFACES. The mechanical operations that 
are required to finish a surface are Boring, Broaching, Chipping, 
Drilling, Filing, Milling, Planing, Reaming, Scraping, Shaping 
and Turning. 

The operation may be specified on the drawing for any given 
surface as a guide to the artisan. 

FITTING SYMBOLS. Parts that fit together, as a wheel on 
a shaft and a shaft in a bearing, must have an allowance made 
for tight or loose fitting of the parts. Conventional Fitting Sym¬ 
bols and their uses are shown in Fig. 22. 


/ Trr/A/eSrMBoiS XX fr ^ CE/:r ' T ~ ' S T/ / 

ARBITRARY SYSTEM x E ASyTr,y/-//^ 

//?£7S7/70/e. 

® SUCK/NG F/T-S/7&/Y 

^/T7&//es- /?o/?. 

O SL/D/NG <$ FUNNING F/T 
S/cr/f/ess thcrn/?o/e. 
90 CLEARANCE-A/ot 
. O /* 

P FOL/3H- A/O excztst 

s/ze. 

SCFAFE - To F/Y or- 
/'or- /?ec7ry>7^ st/r7£rce. 
PF FOL/G/Y F//V/S/Y — A/o 
exc?cY s/ze* 

G Gff/A/D ~ 



Fig. 22. 


SECTIONS. 1. As the object of a drawing is to represent 
the exact construction of the machine or part drawn, it is often 
convenient for clearness to draw some of the views or parts of 
them as sections through the object. Thus, in Fig. 16, the upper 
half of the right-hand view represents a section on a plane A—B 
that is normal to the vertical plane of projection. That is, we 
assume the near portion of the upper half of the object (as shown 
in the right-hand view only) to be cut away, back to the section 
plane, showing the construction of the object as it appears at that 
section. 

2. The trace of a section plane must be lettered, in one of 

the views, and a note placed directly under the view stating where 

the section is taken; thus, Section on A—B, Section on X_Y_Z. 

Inclined lower case letters are used for this notation. (See Fig. 23.) 



































25 


3. A section plane may be offset, as shown at A—B—C—D 

in Fig. 23, to include portions of an object that are not in a straight 
line. 

4. When the surface of a section stops at a plane through 
the center line, the center line is made a full line as far as the 
section extends, and shaded if the conditions require it. 

5. When the surface of a section extends a little beyond the 
center line an irregular line (Fig. 13) is drawn to show a fractured 
surface. The latter method is frequently necessary to more clearly 
show the detail of the interior; for example, the key and keyway 
in the illustration, Fig. 16. 



CROSS-HATCHING. 1. All portions of the object cut by 
a section plane are cross-hatched by lines making an angle of 
45°, except where otherwise shown in the “Conventional Standard 
Cross-hatchings” Plate A. Cross-hatching is done after a drawing 
is fully dimensioned, omitting it where the dimension is placed. 

2. All sections of the same piece, in the same plane, are cross- 
hatched in the same direction. Cross-hatching lines are never 
drawn across a full line. 

3. When two or more pieces, of the same or different 
material, show in a section adjacent to each other, the cross- 
hatching must be drawn in opposite directions. (See Figs. 16, 
22 and 44.) 




































































26 


CONVENTIONAL 

STAN DARD CROSS - HATCH INGS 


§1111 

CAST IRON 

||||f 

CAST STEEL 

Wmm 

y/y/y/y/y/y A 

BRASS 

W/MM 
'////////////. 

ALUMINUM 


leather 


A)Cp/v - ——— 

WOOD 

/ //////A / //z. 

V//A///////z 

vy/y/yZv/Z 


RED BRICK 




WROUGHT STEEL 



ASBESTOS 


LIQUID 


vyyyyyyyyyyyyy/. 






FIRE BRICK 

Plate A. 







WROUGHT IRON MALLEABLE IRON 



VULCANITE 



WIRES 



GLASS 



STONE 






































































27 


4. Care should be taken to space the cross-hatching uniformly. 

This is readily done by eye, after a little practice on a separate 
sheet of paper. The appearance of a drawing, which is otherwise 
faultless, is often spoiled by poor cross-hatching. 

5. Cross-hatching lines should be somewhat finer than the 
outline and not too close. Use about a re" space. They may be 
drawn across center lines. 

6. The system of conventional standard cross-hatchings to be 
used in sectioning is shown on Plate A. Note the spacing and 
width of line. 



SHAFT 



WOOD 


n 


> 

n 

l m n 

IRON 

ZJ 




CHANNEL. IRON 


■■i 


BAR 

Z3 

» 

PIPE 

.1 

m v. 


TEE IRON 





I BEAM 


Fig. 24. 


7. Axles, Balls, Bolts, Cotters, Keys, Nuts, Screws, Shafts, 
Spokes of Wheels, Valve Stems, etc., are not cross-hatched when a 
section is taken longitudinally through them, but are drawn full as 
though the cutting plane did not pass through them in order to 
make a drawing clearer. (See Figs. 16, 22 and 23.) 

8. Ribs, Webs and similar thin parts are not cross-hatched 
when a section is taken lengthwise through them. An alternative 
method used to some extent shows every other section line drawn 
across the rib or web. (See Fig. 23 for both methods.) 















































28 


9. A shaft, bar, or other long piece is represented as broken, 

as shown in Fig. 24, when its full length cannot be drawn to a prac¬ 
tical scale. The break should show roughly the outline of the 
cross-section of the piece. 

10. Long structural details are always drawn foreshortened 

(other pieces may be if advisable) without a break showing and 
the dimension marked Not to Scale. (See Structural Drawing and 
Elementary Design by Conklin.) 

TINTING. 1. When a large area of a drawing on paper or 
cloth is in section it is often more convenient to color the section 
than to cross-hatch it. This method is used in Architectural and 
Civil Engineering practice. 

2. A drawing should be fully inked in with water-proof ink, 

freed from pencil marks and well cleaned before the color is applied, 
as the color is readily removed with a pencil eraser. If it is too 
dark a cleaning eraser will tone it down. 

3. A section on paper or the dull side of tracing cloth may 
be colored by rubbing a soft black lead pencil over it. For pro¬ 
ducing distinctive colors the ordinary colored crayon may be 
applied generously and then blended to a uniform tint by rubbing 
the surface with a piece of cloth dipped in gasoline. Any color 
outside of the section is readily erased with an art gum eraser. 

4. Colored inks, standardized, and moist water colors are 
also used for tinting sections. These liquid colors may be used 
sparingly on the dull side of tracing cloth. The cloth will wrinkle 
if too moist. 

5. For tinting sections with moist water colors use the ones 
named for the materials given in the list below. 

The color mentioned first, for a given material, should pre¬ 
dominate in mixing the tint representing that material. In any 
case, a very small quantity of color will suffice. 


Cast iron.Paynes gray. 

Wrought iron. . .Prussian blue. 

Wrought steel.. .Prussian blue and crimson lake. 

Cast steel.Crimson lake and Prussian blue. 

Brass.Gamboge. 

Bronze.Gamboge and crimson lake. 

Copper.Crimson lake and gamboge. 

Babbitt.Water-thinned India ink. 

Leather.Water-thinned India ink and burnt sienna. 

Wood.Burnt sienna. 

Glass.Prussian blue and gamboge. 











29 


6. Go over the portions to be tinted with a brush, using 
clear water, just before applying the tint; this will prevent the 
tint from drying too rapidly. Make the tint light, then, by going 
over it again, if necessary, the proper shade may be obtained. 
Mix the tint in a saucer and stir with every dipping of the brush. 
Remember that the process is that of tinting and not painting. 

7. A smooth tint will result if it is done quickly, working 
from left to right and downward. Keep a drop of tint on the 
paper just ahead of the brush and leave the part tinted practically 
dry. An excess of moisture remaining will cause the tint to dry 
blotchy. If the tint runs over a line, brush back quickly with 
the finger. 

8. When the area to be tinted is quite large, the paper should 
be stretched. This is done by thoroughly wetting the entire 
paper and pasting it, along the edges, to the drawing board, allowing 
it to become thoroughly dry before starting the drawing. 

9. Lines and dimensions may be placed directly on any tinted 
surface if necessary, but cannot be erased without removing the 
tint. 


30 . 


LINE SHADING 




Fig. 25. 





































































































31 


LINE SHADING. 1. Line shading is used to represent more 
clearly or more quickly the contour of the surfaces of which the 
piece is composed. 

2. This method is used where the number of views is limited 

or where it is desired to represent to those who are not familiar 
with the principles of mechanical drawing, the construction of a 
machine or some part it is desired to emphasize. 

3. Book and magazine illustrations and Patent Office draw¬ 
ings are examples in the use of line shading. 

4. The distribution of light and shade found in current practice 
in the case of a circular cylinder can be produced by assuming the 
illumination to come from the opposite sources S and Si (Fig. 25) in 
parallel rays, their vertical projections making 45° with the horizon¬ 
tal plane of projection and their horizontal projections at 45° with 
the ground line. Source S is to the left and back of the observer. 

5. The brightest part of an illuminated object is that which 
reflects the rays of light directly into the eye of the observer. 
Assuming the light to fall as above described, and knowing the 
angle of reflection R must equal the angle of incidence I, reference 
to Fig. 25 will show that the high light element must be 22^° 
around from the center line C L. At this element only, the rays 
of light would be reflected normal to the plane of projection and to 
the eye of the observer. 

6. The dark element, or no light, is 45° around on the opposite 
side of the center line C L, for at this point the light rays are 
tangent and there is no reflected light. Beyond this element 
the surface is slightly illuminated by the rays Si from below. 

7. The limiting elements A B and D E (Fig. 25) are of the 
same shade. The shades received by all surfaces of revolution are 
shown by lines which represent the generatrix in various positions, 
the intensity of the shade being effected by the thickness of the lines. 

8. First, ink the outline of the drawing with a uniform line; 
omit dimensions, dotted lines, shade lines and center lines, although 
the latter are always penciled for construction. Second, ink the 
shading, the straight lines first, and then the curved ones. Avoid 
making lines fine or too close. 

9. Practice line shading different surfaces on a separate 
sheet of paper before line shading a drawing. 

10. Examples of line shading will be found on Plates B, C, 
and D, which cover most shapes met with. Study them and 
apply to your special case. 

11. Do not use a knife on line shading; use a rubber to erase 
errors and restore the surface by rubbing it with a piece of paper. 


32 



Plate B. 


























































































33 



' $ 


A 


B 



R andX to be found by tr/at 

Screw threads that are § or over /h d/amefen when 
drawn to sca/e. shoutd be drawn to the exact shape 
andp/'tch, the carve of the he/ix be/ay ney/ecred, 
and shade as shown at ft andB. When onder §D/an7. 
use the convent/onatmethods £ and £ 


Plate C, 



















































































34 


Draw A~CandA~ B 
” C-DlltoA-B 
Prolong straight 
lines to meet A~B 
With radiiX~A~C 
and ft on DrDdraw 
the arcs. 



Draw A~C andA~B DrawC~DHtoA~B. DrawC-E 
_L toE~H. Draw E~B. Prolong straight fines to 
EE IM'fh rad/i X = CEatid ft on E~D draw the arcs. 


Plate D. 








































































35 



INTERSECTIONS. 1. The intersections of curved surfaces 
should be drawn as an aid to the understanding of a drawing. 
The line of intersection of two pieces must be carefully plotted 
when it is required that one or both pieces be cut to fit together 
at the line of intersection. (See Developments.) 

2. Descriptive Geometry treats of the methods employed in 
finding intersections, but the student unfamiliar with this subject 
can plot most of the simpler ones met with in practice if he observes 
the following instructions. 
































































3. To determine a point on the line of intersection of two 
surfaces, pass a plane through both in a way that its trace on 
each surface will be an element or other known line, these elements 
will intersect at a point on the line of intersection of the surfaces. 

4. A sufficient number of points should be plotted to deter¬ 
mine the shape of a curve of intersection. Approximate the 
curve by drawing a light freehand line through the points plotted, 
as a guide for applying the Irregular (French) Curve. With the 
aid of the Irregular Curve a smooth curving line is drawn through 
the points. 

5. Two intersecting cylinders, A and B, with axes at right 
angles and in the same plane are shown in Fig. 26. I is their 
line of intersection, its shape being determined by plotting points. 

















































37 


These points are the intersections of elements in the cylindrical 
surface A with elements in the cylindrical surface B. Element 1 
of A intersects element 1 of B at l v and element 3 of A intersects 
it at 3 V . Element 2 of A (see end view) intersects element 2 of 
B at 2 P ; 2 V , the projection of this point on the vertical, plane is the 
lowest point on the curve of intersection I. Intermediate points 
are found by passing planes in such a way that they cut elements 
from each surface, the intersection of the elements in any one plane 
being a point on the curve. For example, the plane X—Y at any 
distance S from the center line (see end view) cuts element 4 P 5 P 
from A and 6 h 5 h (see top view) from B. From 5 P and 5 h the pro¬ 
jection 5 V on the vertical plane is determined. This point, 5 V , being 
the intersection of two elements, is a point on the curve of inter¬ 
section. Another point, 7 V , is determined by projection from 7 h . 

6 . Cylinder B (Fig. 26) is hollow and has been broken away 
to show a hole cut through its lower portion. This case is similar 
to the previous one, the difference being that the thickness of 
the cylinder is shown and the surface of the hole therefore inter¬ 
sects the inside as well as the outside surface of the cylinder B. 

7. The plane M—N (see end view) cuts on the cylindrical 
surfaces elements that pass through the points 8 P and 9 P and cuts 
the element 8 P 9 P on the semi-cylindrical surface of the hole. The 
points 8 P 9 P in which the elements meet, if projected on the vertical 
plane, determine 8 V and 9 V , which are points on the lines of inter¬ 
sections J and J'. 

8. A pipe elbow with its center at O, intersected by an 
offset cylindrical outlet, is shown in Fig. 27. In this case points 
in the line of intersection I are found by passing planes containing 
elements of the cylindrical surface and arcs on the surface of the 
elbow. Element 2 appears to intersect the elbow at b p , end view, 
but a plane passed through 2 cuts from the elbow, front view, 
the arc b v 2 v c v . This arc is found by projecting the point b p to b v 
on the center line through O, thus determining a point in the plane 
through which to draw an arc with O as its center. The element 2 
lies in the plane of this arc and intersects it at 2 V , which is a point 
on the line of intersection 1 V 2 V 3 V . The point 2 V projected to the 
end view determines 2 P , a point on the intersection that appears 
in that view. Pass any other plane, as X—Y, at any distance 
S from the center line. The points of the lines of intersection 
that lie in this plane are 4 V and 5 V in the front view and 4 P and 5 P 
in the end view. A sufficient number of points are to be found 
through which smooth curves of intersection may be drawn. 


38 


9. Note that between 6 V and 7 V , front view, the line of inter¬ 
section replaces a portion of the arc of the elbow in this view. 
This is due to a portion of the cylindrical piece, 6 h 8 h 7 h top view, 
6 P 8 P 7 P end view, overlapping the center of the elbow. 

10. A bell-shaped surface of revolution (B) intersected by a 
plane surface (S) and a cylindrical surface (C) is shown in Fig. 28. 
(Heavy lines given light ones to be found.) Any cutting plane, 
as X—X, passed perpendicular to the axis of revolution will cut an 
arc of radius or 2 h on the surface of revolution and a straight line 



Fig. 28. 


element 2 P 2 P on the plane surface; this arc and element lie in the 
same plane and intersect at points 2 h and 2 h (projected from 2 V ) 
which are points on the line of intersection of the two surfaces 
(B and S). l h and 3 h are the limit points of this line and its shape 
on the profile plane will be given by the points l p , 2 P , 3 P found by 
projection. Any cutting plane, as Y—Y, cuts an arc of radius 
or 6 h on the bell surface and elements 6 P 4 P at 6 P (side view) on the 
cylindrical surface, also an element at 4 V on the plane surface. 
Project 4 h 4 h from 4 V and 6 h 4 h from 6 P , The elements 6 h 4 h and 4 h 4 h lie 
in the same plane and intersect at 4 h , which is a point on the line 




































39 


of intersection of the cylindrical surface (C) and plane surface (S); 
3 h , 5 h and 3 h are the limit points of this line. The element 6 h 4 h 
and arc of radius or 6 h lie in the same plane and intersect at 6 h , 
which is a point on the line of intersection of the bell surface (B) 
and the cylindrical surface (C); 3 h , 7 h and 3 h are the limit points 
of this line and its shape on the vertical projection will be given 
by the points 3 V , 6 V , V found by projection. Read paragraph 4. 



DEVELOPMENTS. 1. The development of surfaces is 
necessary when sheet material is required to be cut to fit together. 

The line of intersection of the surfaces must first be determined 
and from it the development plotted. 

2. An elliptical shaped piece intersecting one of square sec¬ 
tion is shown in Fig. 29. In this case an auxiliary view A is 
required to show the true size and shape of the elliptical piece. 
The line of intersection l v , 2 V , 3 V , 4 V , etc., was determined by planes, 
as X—X, passed parallel to the axis of the oval piece. These gave 
elements as 6-6 v intersecting elements as H-6. 

















































40 


3. To plot the development of the elliptical piece draws a base 

line 1, 2, 3, 4, .... 13,.1 and make 1,2 equal to 1 A 2 A measured 

on the arc by stepping off carefully with a bow spacer, make 2,3 = 
2 a 3 a , etc. Draw the elements l,l v , 2,2 V , etc., perpendicular to the 
base line and equal in length to the corresponding element on the 
vertical projection. A smooth curve drawn through the points 
1 V ,2 V ,3 V , etc., plotted on the developed surface of the elliptical 
piece will give the shape the piece must be cut to fit the opening in 
the square piece. The opening is plotted in a similar manner. 



ISOMETRIC DRAWING. 1. An Isometric Projection of a 

cube is one in which all lines of the cube are of equal length, (isos 
equal + metron, measure). 

2. Orthographic Projections, 3d angle, of a cube in three posi¬ 
tions are shown: first, in Fig. 30, with all faces parallel to the 
planes of projection; second, in Fig. 31, rotated through 45° about 
a vertical axis 0 2 ; third, in Fig. 32, rotated about a horizontal axis 
0 3 until its diagonal (1-7) is perpendicular to the vertical plane. 
The vertical projection of the cube in this position is an isometric 
projection, since all edges of the cube are equal in length. The 
edges are shorter than the true length on the cube. 

3. Isometric Planes are the three dimension planes of the 
cube visible in its isometric projection. (See Fig. 33.) 

4. Isometric Axes are the lines of intersection of the isometric 
planes and are at 120° with each other. (See Fig. 33.) 

















41 


5. Isometric Lines are lines that are perpendicular to either 
isometric plane H, V or P, Fig. 33; they are measured in their 
true length parallel to the axes. Non-1 so metric Lines must be 
plotted by the Orthographic Coordinates of points in the lines. 

6. Isometric Projections of Circles that are parallel to the 
Isometric Planes will be ellipses. The lengths of the major and 
minor axes are not known, as they are in the ellipse which is the 
oblique projection of a cylinder or cone. (See Geometric Drawing, 
Plate V, for drawing an ellipse with axes given.) 



Fig. 32. 


Fig. 33. 


7. A circle inscribed in the face of a cube will touch at the 
four diameter points D (Fig. 35). Any points in the circle, as A, B, 
E, M, N, can be projected on an Isometric Plane by laying off the 
coordinate distances for each point parallel to the Isometric Axes 
of the circle plane, as Xi—A and Yi—A for point A in Fig. 34. If 
the circle had a dip in it at B to B' perpendicular to its plane and 
then slanted up to E (a situation impossible to show in the one 
view of Fig. 35) the point B' would have to be determined by a 
third dimension, as B—B', Fig. 34, laid off downward parallel to 
the vertical axis. The slant line will be the one drawn from B' to E. 
B—B' is an Isometric Line and B'—E a Non-Isometric Line plotted 
by the Orthographic Coordinates of its points. It should be 




















42 


noted that the four 45° points F, of the circle, always fall on the 
major and minor axes of the ellipse. (See Fig. 34.) 

8. To draw the Isometric of a circle plot its center on the 
drawing and draw through it the two diameter lines D—D parallel 
to the isometric axes in the plane of the circle. Draw lines through 



METHOD L- NEARLY ACCURATE 

METHODS OF DRAWING ISOMETRIC PROJECTIONS CIRCLES 

SEE GEOMETRIC DRAWING FOR METHODS OF DRAWING TRUE 
AND APPROXIMATE ELLIPSES IF THE LENGTHS OF AXES ARE GIVEN 

Fig. 34. 

the diameter points D parallel to the diameter lines, a line through 
their intersections L and L will determine the direction of the 
major axis of the ellipse and one through S and S the direction of 
the minor axis. The ellipse may be drawn by one of the three 
methods shown in Fig. 34, the three-point method, being easiest, is 
preferred. The arcs in this method are drawn in the order of the 
radii Ri, R 2 , Ra. See paragraph 9 for details of this method. 




















43 



9. The Isometric three-point ellipse may be constructed quickly 
by drawing lightly, with C as the center, a circle whose diameter 
D—D is equal to the circle to be projected. The four diameter 
points D and the two S points will fall on this circle and, as shown 
in Fig. 36, they can be readily located with a triangle and are the 
points required to construct the ellipse. Point Q is R 2 from C. 

10. An Isometric Drawing of a portion of a drawer is shown 
in Fig. 37. This illustrates the application of the isometric circle 
in each of the planes and the method of centering a drawing. 



THE LINE 0-C-D-E IS 
USED ONLY FOR LAYING OU 


AN ISOMETRIC 
DRAWING 
SHOWING THE. 
CONSTRUCTION 
OF>A DRAWER 
AND 

The methodof 
dimensioning an 

ISOMETRIC DRAWING. 

THE LINE 4 IS A CENTER LINE 
OF SOLID. THE LINE A-0-C-D-E 
IS A CENTER LINE OF SURFACE. 


Fig. 37. 




















44 


SKETCHING. 1. For Freehand Machine Sketching the 
following materials are required: 

Sketching outfit: 

Sketch board, 14" x 9 " x fiber. 

Steel clip, 2 \" Bull Dog type. 

Pad cross-section paper, A x iV' ruling. 

H lead pencil, Mongol or Venus. 

Pencil eraser, E. Faber No. Ill Emerald. 

2-ft. boxwood rule, Stanley No. 59. 

Pair 6" firm joint inside calipers, B. & S. make. 

2. The object of a sketch is to give, in as few views as are 
necessary, sufficient information as to the shape and size of the 
machine or the part represented to enable a draftsman to make 
complete working drawings. Sketches are made freehand on 
cross-section paper; unruled paper is used when the sketcher is 
an adept. 

3. Each sketch sheet must contain the name of the machine, 
the name of the piece, quantity required, material, finish, and 
the part number. (See Figs. 38 and 39.) 

4. Each sketch sheet should contain sketcher’s name, date 
sketch was completed and total time consumed in sketching all 
views of each piece placed as shown on Figs. 38 and 39. 

5. The size of the sketch need not be in proportion to the 
size of the object, but should be large enough to contain all dimen¬ 
sions without being crowded. Clearness is essential in sketching. 

6. Parts are to be sketched separately, not assembled. 

7. The piece should first be sketched by eye, endeavoring to 
maintain its relative proportions before taking any measurements. 

8. The dimension lines with arrow heads are then placed 
where the dimension figures will show to the best advantage. 
Finally the piece is measured and the dimensions placed in the 
spaces previously provided. 

9. Sketch the views of one piece only on a sheet, until other¬ 
wise instructed. When the piece is large or complicated, each 
view should be placed on a separate sheet. 

10. In sketching large pieces one view may extend over two 
or more sheets of the sketch paper. The portion of the view 
on each sheet must begin and end at a center line or other fixed line 
on the object. 

11. If more than one sheet is required, to properly portray the 
piece, page the sheets in the lower left corner as shown in Fig. 38. 


45 


12. In general, the same views, sections, etc., which would 
be used in making working drawings are used in sketching, except 
that in sketching many abbreviations are used to simplify the 



work. For example, in Fig. 39 only one view of each detail is 
shown, the plan being omitted, and the abbreviations Diam. and 
Hex. added after the dimensions to indicate that those portions 
























































































































































46 


are round and hexagonal. In the same way Sq. for square, Oct. 
for octagonal, and other abbreviations are used. (See Abbre¬ 
viations, Fig. 20.) 

13. When a piece is symmetrical about an axis, a view of 
one-half of it is sufficient. (See Fig. 38.) By taking advantage 
of these and similar points, both time and labor are saved. 

14. Directions given for dimensioning drawings are appli¬ 
cable to sketches, although it is better to give too many dimen¬ 
sions than too few, as one does not always have access to the object 
when he makes the working drawings from the sketches. 

15. Rough castings should be measured to the nearest six¬ 
teenth and allowance made for draft, when this affects the required 
measurement. 

16. Judgment should be exercised when making measure¬ 
ments, especially of rough work, as an apparently odd dimension 
may be due to the irregularities of casting or forging. On finished 
work, measure as closely as possible. 

17. Dimensions should be referred to center lines and to 
finished surfaces rather than to rough ones. 

18. The radii of all curves should be given. To ascertain 
these, take a piece of paper and with a pencil mark the outline of 
the curve upon it, and then with a pair of calipers, used as dividers, 
obtain the correct radius. When this cannot be done, take a wire 
or thin strip of lead and bend it around the curve, and with the 
aid of this mark the outline on paper and proceed as before. 
Irregular curves and non-circular arcs should have their ordi¬ 
nates and abscissas given for use in plotting the curves on a 
drawing. 

19. Holes should always be located by their centers. Where 

there are several holes of the same size, similarly located in a piece, 
it is not necessary to give the diameter of more than one of them. 
When measuring the depth of drilled holes, give the distance to 
the point where they begin to taper. (See H on Fig. 45.) 

20. Tapering and tapped holes should always be noted. The 

number of threads will be understood to be standard unless other¬ 
wise noted. 

21. To dimension a cavity from which the open calipers 
can not be extracted, scratch a cross on each leg of the caliper 
and, measuring the distance between their centers, extract the 
calipers and adjust the crosses to this same distance. The meas¬ 
urement across the caliper points is the one desired. 


47 



Fig. 39. 




























































































































































































































































48 



Plate E. 





































































49 


LETTERING. 1. Special attention should 
be given to lettering, as, when well executed, 
it adds greatly to the working value of a draw¬ 
ing. With care and constant practice one can 
do satisfactory lettering. 

2. Bold single-stroke letters are desirable. 
They are easily made, look well and are appro¬ 
priate on mechanical drawings. 

3. The lettering on all drawings, unless 
otherwise directed, is to be done according to 
the system described in Reinhardt’s “Free¬ 
hand Lettering” (see Plate E), using inclined 
and upright letters of the “Gothic” type in 
the three heights shown on Plate F. 

4. For the small lettering in descriptive 
matter, notes, dimensions and arrow heads 
a “Gillott No. 390” pen should be used. 

5. For the main title, large letters and 
when filling in, a “ Hewitt’s Patent Ball Pointed 
Pen,” Leonard’s No. 516F, is most suitable. 

6. Notes and descriptive matter should 
read from the Lower or Right-hand edge of 
a drawing and not in a diagonal direction. 

7. Index numbers on tracings are of the 
block type shown in Fig. 40. 

8. Ruled letters and figures are shown in 
Fig. 41. 




Fig. 41. 


Fig. 40. 



























































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51 


TITLES. 1. Every drawing should have a general title 

(see Plate G) containing the following essential information: 

NAME OF THE PIECE. 

NAME OF THE MACHINE OF WHICH IT IS A PART. 

QUANTITY REQUIRED, MATERIAL, FINISH. 

SCALE, NAME OF DRAFTSMAN, DATE COMPLETED. 

TRACED—(NAME) CHECKED —(NAME) 

APPROVED-(NAME) DATE —(NUMERALS) 

2. Any one piece of a machine is a detail of that machine, 
strictly speaking, but should not be designated as such in the title. 
Name it in the title when no other parts are drawn. When several 
pieces of a machine are drawn separately on a sheet, it then becomes 
a detail drawing and should have a general title as follows: 

DETAILS OF 

NAME OF THE MACHINE OF WHICH THEY ARE PARTS. 

SCALES. NAME OF DRAFTSMAN. DATE COMPLETED. 

TRACED—(NAME) CHECKED —(NAME) 

APPROVED-(NAME) DATE—(NUMERALS) 

3. Part numbers are frequently used as a substitute for names 
of pieces on a detail sheet. These numbers are necessary when 
the pieces are difficult to name concisely or are numerous and 
similar. “PART NUMBER —” replaces “NAME OF PIECE” in the sub¬ 
captions. On the assembly drawing the numbers must appear in 
circles with leaders to the parts designated. (See Fig. 5.) 

4. The Location of the Title on Drawings is shown on Forms 2, 
3 and 4, under size of sheets, and on Plates G, J and K. 

5. Titles should have a symmetrical appearance, and each line 
of words should vary in height according to their importance. 

SUB-CAPTIONS. 1. A sub-caption is to be placed under 
each piece on a detail sheet (see Plate H); it should contain 
the following essentials: 

NAME OF PIECE. 

QUANTITY REQUIRED, MATERIAL, FINISH. 

SCALE. 

2. If the scale is the same for all the details it should be 
omitted from the sub-captions. Avoid using more than three scales. 

BILL OF MATERIALS. 1. A list should be placed on drawings 
that show several pieces assembled. Its form should be as shown 
on Plate H or J and contain the following essentials: 

BILL OF MATERIALS. 

PART NO., PRINCIPAL PIECE, QUANTITY REQUIRED, MATERIAL, FINISH. 

PART NO., SECONDARY PIECE, QUANTITY REQUIRED, MATERIAL, FINISH. 

PART NO., SMALLEST PIECE, QUANTITY REQUIRED, MATERIAL, FINISH. 

2. The words “QUANTITY REQUIRED” in the TITLE on an assembly 
drawing mean the number of units wanted. A unit being an 
assemblage of all the pieces specified in the BILL OF materials. 

3. When a BILL OF MATERIALS is given substitute the words 

“AS SHOWN” for “MATERIAL, FINISH” in the TITLE. 


52 









































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56 



Plate K. 

































57 


ASSEMBLY DRAWINGS. 1. When a portion or the whole 
of a machine is drawn showing the various parts joined together 
in their relative positions, it is known as an assembly drawing. 

2. In laying out the drawing of a machine the designer makes 
the assembly drawing first, the details being drawn out to larger 
scales afterwards. On assembly drawings it is often well to show 
sections on different parallel planes in the same view. 

ERECTING DRAWINGS. 1. Erecting drawings are those 
which show all the parts of the machine in place, but neglect the 
unnecessary and minute details of construction. They are fre¬ 
quently drawn to a scale smaller than that of the original design. 
They are use to assemble the fabricated parts and are sent with a 
machine to be used in setting it up at its destination. 

2. Erecting Drawings should have sufficient dimensions to 
enable the erectors to distinguish and place the various parts in 
their proper relation to each other. 

TRACINGS. 1. For reproducing drawings, without injury to 
the original, tracings of them are made upon tracing paper or cloth. 

2. Tracing cloth or linen is used almost exclusively, owing to 
its wearing qualities. It is a specially sized and calendered fabric, 
having one side glazed and the other rough, the former being 
known as the smooth side, the latter the dull side. Tracings can 
be made on either side of the cloth, but the side used should be 
thoroughly rubbed with powdered chalk or soapstone to remove 
greasiness and permit the ink to “take” more readily, the excess 
chalk must be thoroughly cleaned off before starting to trace. 
Tracings partly inked may be rubbed with powder, if the ink 
fails to take, without injury to the lines. 

3. The dull side of the cloth is to be used for all tracings 
unless otherwise directed. It is easier to draw pencil lines on the 
dull side when making additions to views or checker’s corrections. 
Drawings traced in ink on the dull side will make the tracing lie 
flat after removing from the board and not roll up, an objectionable 
feature caused by drawing on the smooth side. 

4. Heavy black lines are required on tracing cloth. (See 
thickness at middle of full line, Fig. 13.) Light, in printing, will 
burn through fine thin lines, causing a blue-print to appear blurred 
and indistinct. (Read “Inking In,” paragraph 3.) 

5. Lines on tracings are not shaded. All lines are drawn heavy. 

6. When lettering a tracing rule pencil guide lines and print 
all lettering without any attempt at tracing it. 


58 


7. Ink may be erased from tracing cloth, the pencil eraser 
usually being sufficient. The ink eraser should be used with care 
to avoid cutting the fabric. Place a triangle or other hard-surfaced 
article under the cloth when erasing. Wherever an erasure has 
been made, the place should be rubbed with a soapstone pencil 
or powdered chalk before re-inking to prevent the ink from passing 
through the cloth. The powder must be removed before the ink 
is applied. 

8. Ink dropped upon tracing cloth should never be blotted, 

but should be smeared as quickly as possible with the thumb, 
using a scooping-up motion. When the smear has dried it is 
readily erased with the pencil eraser. 

9. Pencil and crayon marks can be removed from tracing cloth 
with the Art Gum cleaner without affecting the ink lines. 

10. Trim tracings as directed in “Trimming” instructions. 

BLUE-PRINTS. 1. Original drawings are seldom sent into 
the shop. Duplicates in the shape of either blue-prints (white 
lines on a blue ground) or white prints (blue or black lines on a 
white ground) are used in place of them. 

2. Blue prints are moderate in cost and can be produced in 
endless numbers. They are obtained by exposing a sensitized 
paper or cloth to light rays. A positive tracing of the original 
drawing on a translucent medium, such as tracing cloth or paper, 
is interposed between a light and the sensitized paper and in 
direct contact with the latter, the time of exposure depending i, 
upon the intensity of the light and the composition of the sensitizing 
emulsion. 

3. The age, or length of time the paper has been sensitized, 
modifies the time of exposure. The fresher the paper, the less 
exposure required. The prints are fixed by immersing for about 
ten minutes in clear water. Special papers require the addition of 
chemicals to the fixing bath. Instructions for the treatment of 
such papers generally accompany them. 

4. Blue-Print Paper, and other sensitized papers, are obtain¬ 
able in different grades of stock and different weights. Light 
weight paper is used for prints that will require very little usage 
or for prints to be mailed. Heavy weight tough papers are used 
for prints requiring rough or frequent handling. 

GEARS. 1. Conventional lines and notations for spur and 
bevel gears will be found on Plates L and M. 

22. For the theory of gearing and method of drawing various 
types of gear wheels, refer to one of the many text-books on the 


59 


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Plate 


































61 


subject. George B. Grant’s “Treatise on Gears ,” and Brown 
& Sharpe’s “Practical Treatise on Gearing” and “Formulae in 
Gearing,” are published by the manufacturers. 


SCREW THREADS. 1. A helix or screw curve is the path 
of a point moving on the surface of a circular cylinder, the motion 
of the point around the axis and paral¬ 
lel to the axis being uniform. 

2. The method of drawing the helix 

is shown in Fig. 42, the true shape of 
a V and a square thread being shown. 

When drawing screw threads, except 
for very large diameters, it is not 
necessary to lay down the curve of the 
helices of which they are comprised. 

Straight lines properly drawn from point 
to point and root to root answer all 
practical purposes. (See Fig. 43.) 

3. To draw a screw thread, lay off 
the pitch of the points accurately on 
one side. Draw shape of threads on 
that side. Locate any one point on 
opposite side. Draw the point line 
across, then draw all point lines parallel 
to this one. Draw shape of threads on 
opposite side. Draw root lines across. 

This is the quickest, most accurate and 
practical method of drawing threads. 

4. A right-hand thread is one that 
will cause a threaded piece to advance 
into a tapped hole when the piece is 
turned clockwise. (See Fig. 43.) 

5. A left-hand thread is one that 
will cause a threaded piece to advance 
into a tapped hole when the piece is 
turned counter-clockwise. (See Fig. 43.) 

6. To determine a thread let the 
threaded piece be held horizontally with 

the axis at right angles to the body, the threads seen will incline 
away from the body from left to right for a right-hand thread and 
from right to left for a left-hand thread. Threads seen in a section 
are the reverse of this. (See Fig. 43.) 

7. Threads are understood to be U. S. standard, single and 
right-hand unless otherwise specified. Standard shapes are 
shown in Plates N and O. 



k-ROOT diam.- 
-DIAM OF 5CREW- 

Fig. 42. 















































62 


RIGHT HAND INSIDE. AND OUTSIDE SCREW THREADS 


SINGLE V. DOUBLE V. SINGLE SQ. DOUBLE SQ. 



5INGLE V. DOUBLES/ SINGLE SQ. DOUBLE SQ. 


LEFT HAND IN5IDE AND OUTSIDE SCREW THREADS 

Fig. 43. 

8. The pitch of a single thread is the distance between two 
adjacent points. It is the distance a point would advance parallel 
to the axis in one revolution of the thread (Fig. 42); e. g. t single 
thread pitch, 4 pitch, or 4 threads per inch are the same. 

9. The lead of a double, triple or other multiple thread is 
the distance from one point to the next point of the same thread. 
(See Fig. 43.) The distance between two adjacent multiple 
threads is sometimes called the divided pitch. The lead is more 
generally specified. 

10. Multiple threads are noted thus: Double thread 
lead, or Double thread 2 pitch; Triple thread f" lead, or Triple 
thread 1J pitch. Triple thread 3 pitch, means three threads each 
making three revolutions per inch. 




























































63 


11. The diameter of a thread is the extreme outside diameter 
of the threaded portion of a piece. (See Fig. 42.) 

12. Screw threads 
in a section are drawn 
as shown in Fig. 44. 

Note that at B the point 
and root lines are not 
drawn across the section, 
and that those drawn at 
C and A are in back of 
the section. 

13. Hidden threads 
are always represented by 
parallel dotted lines. (See 
nuts, Fig. 16, hole, Fig. 45, 
and bolt in Fig. 46.) 

TAPPED HOLES. 1. The diameter of a tapped (threaded) 
hole is the outside diameter of the threaded piece that would fit 

that hole, not R the 

apparent diameter of the 
hole. (See Fig. 45.) 

2. Drill size for tap 
is the diameter of the 
hole which is drilled to 
prepare it for the tap and 

which leaves the proper 
amount of stock for 
threads. Drills have a 
conical point which is 
118° or, for all practical 
purposes on a drawing, 
120°. Fig. 45 shows the 
shape of the bottom of 
a hole which has been 
drilled. The hole in this 
case has not been tapped 
to its full depth. 

3. A section through 
a threaded hole shows 

the threads at the back of the hole inclined in the opposite 
direction to those in the portion cut away. A little thought with 
reference to Figs. 42, 43, 44 and 45 will make this clear. 





\ 


k 

_ 

_ x' 

f 


0=DIAM OF TAP 
R — ROOT DIAM. 

D = DRILL DIAM. 

- H - DEPTH DRILLED. 

T- DEPTH TAPPED. 
D=R, APPROXIMATELY. 
HIDDEN THREADS ARE 
ALWAYS INDICATED AS 
SHOWN AT X. 


^ V///' 

H 

T 

h 

1 

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l! 

1 i a 

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4 

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Fig. 45. 




































































64 


4. Tapped holes are shown by two circles, the inner one 
full and the outer one half full and half dotted. (Figs. 45 and 46.) 

5. All threaded holes should be designated by a note stating 
the diameter or size of tap and number of threads per inch, 
f" Tap means that the hole is to be tapped to take a screw f" 
in diameter. 

CONVENTIONAL THREADS. 1. This method of showing 

screw threads is to be used, for clearness and economy, when the 
diameter of a thread, as drawn, measures less than f" on straight 
threads (see Fig. 46) and less than 1" on pipe threads (see Plate S). 

2. Conventional threads are used to indicate threads of all 
types. It is not necessary that the number of conventional 
threads should correspond with the actual number of threads 



on the piece. If the thread is other than the U. S. Standard, or 
if the number of threads does not correspond with the standard 
number for the given diameter, there should be a note to that 
effect, thus: “13thds per inch,” “Square Threads 4 per inch,” 
“Double Square Thread 2 pitch,” “Triple V Thread j" Lead,” 
T Pipe Thread,” “Taper Thread 14 per inch, taper x in. per ft.,” 
“Acme Thread 4 per inch.” 

3. The spacing of conventional thread lines should be done 

by eye ; pencil lines may be drawn to limit the length of the heavy 
root lines. The inclination of the lines should be practically the 
same as though the thread were drawn out to its actual shape. 
That is, for a single thread a point on one side should be diametrically 
opposite the adjoining root. For a double thread the point on 
one side should be diametrically opposite the point of the next 













































65 


thread. For triple threads the point on one side is diametrically 
opposite the next root but one. Fig 43 will make this clear. 

4. Conventional threads are not to be used on a section show¬ 
ing two pieces screwed together and both cross-hatched, as A, 

Fig. 44, or on a section showing an isolated outside thread, as B, 
Fig. 44. Isolated inside threads, as C, Fig 44, may be drawn 
conventionally as stated in Paragraph 1. 

CORED HOLES. 1. Cored, bored, counter-bored, counter¬ 
sunk and spot face holes must be so noted, the method and the 
required dimensions for each case are shown in Fig. 47. 



Fig. 47. 


SCREW THREAD PROPORTIONS AND TABLES. The 

standard forms and proportions of screw threads in practical use 
in the United States will be found on Plates N and O. 

BOLTS. 1. The standard proportions for Bolt Threads, 
Heads and Nuts shown on Plate P and tabulated on Plate Q, 
were adopted by the Franklin Institute, December, 1864. The 
sizes for bolt heads in Plate Q are a manufacturer’s. 

2. Manufacturers have deviated slightly from these propor¬ 
tions, owing to the materials used in their, manufacture not being 
commercial sizes. 

3. When drawing bolts and nuts, take dimensions from table 
on Plate Q and use the method shown on Plate P for approximating 
the curves which are, in reality, portions of hyperbolas, the results 
of chamfering. 







































66 





i n 

o 

3 

Ll O 

o 

g S i2 

- 

u H O lo 

" 11 or vs 

Q Q if 

u w^> 
OMC-lcoX 

E£t2rI 

oo^S> 

x 5 u^e-s- 

^ t 2 ' P 7 

a. o t^o*^ 
1 „ “ 


I 
< 

3 ^ 
hi ") 

u 

Ld u 
L. 11 

v9 
X 

<\j 


N T >0 >0 


B « 5 if "J 


NO 

or 

THDS 

-IN 

T 

-IN 

T 

T- 

T* 

-IN 

ro 

-|N 

•0 

-it 

fO 

CO 

(0 

DRILL 

HOLE 

FOR 

TAP 

=JS 

r'lcO 

-rt£ 

N 

>oi5 

N 

-IN 

N 

-o|T 

N 

iolin 

N 

-oi5 

m 

r^tT 

Ml'S 

<o 

TAP 

DIAM 

rvj 

-IT 

N 

-|CV» 

OJ 

<oiT 

CJ 

fO 

-IT 

rO 

—IN 

m 

rOlT 

ro 


NO 

OF 

THDS 

<n 

00 


r- 

vS 



>0 

-IN 

t 

DRILL 

HOLE 

FOR 

TAP 

JlS 

«0|V» 

oiiT 

u>l$ 

«ol5 

-|c0 

gj 


2]_Sj 

fflS! 

TAP 

DIAM 

NoO 


-ICO 

-IT 

(O|<0 

-IN 

>010) 

NIT 

MCO 

NO 

OF 

THDS 

O 

04 

00 


T 

N 

N 

- 

- 

O 

DRILL 

HOLE 

FOR 

TAP 


51$ 

<M# 

nIo 

*oiT 

Nlv® 

SIS 

-In 


SIS 

TAP 

DIAM 

-IT 

>0l5 

-0|o0 

N* 

-IN 

<nl5 

>o|o0 

=|55 

nit 

CO 

NO 

OF 

THDS 

-IN 

T 

-IN 

T 

t 

T 

-IN 

«n 

-IN 

<0 

-IT 

rO 

«0 

DRILL 

HOLE 

FOR 

TAP 

*0|N 

Nl»*l 

-IN 

»0lf0 

N 

HS 

N 

T-lS 

-N 

N 

«l« 

rO 

•rna 

<0 

tf>l5 

(O 

TAP 

DIAM 

N 

-IT 

f\J 

-IN 

N 

r0|T 

M 

m 

-IT 

CO 

-IN 

00 

NlT 

co 

T 

NO 

OF 

THDS 

<n 

CO 

N 


O 

O 

-IN 

>o 

IA 

>0 

DRILL 

HOLE 

FOR 

TAP 

?$ 

mn 

nIco 

L0j-J» 

< 

=4 

21$ 

(OiN 

—1(0 

-IN 

>0100 

TAP 

DIAM 

N|00 


-ICO 

-IT 

»0|C0 

-IN 

‘OlflO 

*lT 

N|cO 

NO 

or 

TH DS 

O 

N 

oo 


T 

CO 

N 

- 

- 

0 

DRILL 

HOLE 

FOR 

TAP 

<n|5 

-IT 

<ni* 

-Jv® 

xR 

tit 

<OjN 

-1(0 

(oiT 

ro|vS 

NiT 

(OlvP 

>0|CQ 

TAP 

DIAM 

- - 

-IT 

•OlJ 

">|«0 


-IN 

*15 

>o|oo 


n|T 

r 


Plate 




























































67 


SQUARE THREAD 



/? = PITCH OF THREAD « 1 + NO. OF THREADS PER INCH. 

DEPTH OF THREAD » 

D- OUTSIDE DIAM. 

^/-EFFECTIVE DIAM. AT ROOT -Z?-/? 


DIAM OF 

SCREW 

l 

4 

5 

1 6 

3 

8 

7 

/6 

a 

5 

8 

3 " 

4 

7 

8 

1 

'5 

4 

'1 

■i 

THREAD5 
PER INCH 

IO 

3 

8 

7 

► 



4 

4 


3 2 

3 

. 3 

DIAM OF 
SCREW 

>§ 

'4 

'I 

a 

4 

4 

*4 

3 

4 



4 


THREADS 
PER INCH 

4 

4 

2 i 

4 

2 

2 

-4 

'1 

'1 

'1 

'£ 

4 



ACME STANDARD THREAD 

-— p —A 



p = PITCH OF THREAD = ItNO. OF THREAD'S PER INCH. 

0— OUTSIDE DIAM. OF SCREW. c/=> DIAM. OF SCREW AT ROOT 



NUMBER OF 

~lh 



THREADS 

DEPTH OF 

WIDTH AT 


PER INCH 

THREAD 

POINT 


1 

.5/00 

.3 707 



.3850 

.27 80 


z 

.2 600 

. 1 853 


3 

.1 767 

. 1 235 


4 

.1 350 

. 0327 


5 

.1 1 00 

.0741 


6 

.0933 

.0618 


7 

.08 14 

.0529 


8 

.0725 

.0463 


3 

.0655 

.041 3 


IO 

.0600 

.037 | 


DEPTH OF THREAD 

d= D-zh =D 

WIDTH AT POINT 


£X N0.THD5.PER IN. 

I 


+.01 


NO.OF THD5 PER IN 
.3707 


+02 


NO. OF THD5. PER IN. 

rO DRAW THE ACME THREAD, FIRST 
LAYOFF THE SUCCESSIVE PITCHES, 
FROM THESE POINTS MARK OFF THE 
POINT WIDTHS f. THR0U6H THE TWO 
SETS OF POINTS THUS FOUND 
DRAW LINES AT 30 AS SHOWN. 
THIS IS SUFFICIENTLY CLOSE FOR 
A DRAWING. 


Plate O. 



















































































68 



Plate P, 

















































































69 


PROPORTIONS FOR U.S. STANDARD 

SCREW* THREADS "AND nuts 

HOOPES AND TOWNSEND'S STANDARD SIZES FOR BOLT HEADS 


DIAM 

OF 

BOLT 

D 

BOLT THREADS 

NUTS 

HEADS 

THDS. 

PER 

INCH 

•N 

DIAM. 

AT 

ROOT 

d 

AREA 

AT 

ROOT 

A 

THICK 

HEX. 

OR SQ- 

T 

HEX. 

LONG 

DIAM. 

C 

5Q. 

LONG 

DIAM. 

C 

HFX.5Q. 

SHORT 

DIAM. 

F 

HEX.OR SQ. 

COUNTERSUNK 

SHORT 

DIAM. 

F 

THICK 

H 

DIAM. 

K 

THICK* 

H 

» 

4 

2 O 

.1 83- 

.02 6 

j_ 

37 

64 

AS 

64 

1 

2 

3 

8 

3 

16 

J_ 

2 

1 

8 

5 

!6 

1 8 

.ZAO 

.045 

5 

/ 6 

M 
/ 6 

27 

32 

19 

32 

IS 

32 

IS 

64 

9 

16 

3 

16 

3 

e> 

1 6 

.294 

.067 

3 

8 

5 1 
64 

63 

64 

1 / 

16 

9 

16 

9 

32 

/ / 

16 

3 

16 

7 

16 

1 4 

.344 

.092 

7 

/6 

7 

© 

»4 

25 

32 

2 1 
32 

2 _l 

64 

3 

4 

7 

16 

1 

2 

1 3 

400 

.125 

J_ 

Z 

1 

1 ' 5 
‘64 

7 

8 

3 

4 

3 

a 

7 

8 

1 

4 

9 

16 

1 2 

.454 

./ 6 1 

9 

/ 6 

1 8 

■a 

3/ 

32 

2 7 

3 2 

27 

64 

15 

16 

1 

4 

5 

8 

1 1 

.507 

.201 

5 

8 

'it 

«i 

■ it 

1 5 

1 6 

15 

32 

■i 

1 

4 

3 

A- 

10 

.62 0 

.30/ 

3 

4 


,42 

64 

•± 

■± 

9 

16 

•i 

3 

8 

7 

6 

9 

-73/ 

.419 

J7 

8 

•H 

2 ^- 

32 


'if 

21 

32 

'1 

7 

16 

1 

<3 

83 _r 

.550 

/ 

'I 

^ a 

'I 

*T 

3 

4 

'1 

1 

2 


7 

.940 

.693 


2 A 

2 Fg 

|L3 

1 16 

<ri 

27 

3 2 



7 

LOGS 

.890 

'i 

2 — 
^16 

2— 

^ 64 

2 


1 5 

1 6 

't 

6 

1.1 GO 

1.056 

'1 


3 — 
32 

4 ,\ 

4 A 

>k 

•i 

6 

1. 284 

1.294 



3^^ 

64 

2| 

4 ± 


-i 


1.389 

1.5/5 

/£ 

' 8 

2 . — 
32 

3 — 

3 8 



•A 

\ 

ir~7 


5 

1.49 1 

1.746 

'1 

3 — 
°/6 

3 64 


2 — 

* 8 


jt 



■*-D-* 


5 

1.6 1 6 

Z.05I 


3 i* 

32 

4 — 
32 

‘If 

2 ii 

C IG 

■3 

2 


1.7 12 

2.301 

2 

*i 

4 — 
^64 


3 

4r 

- 



1.962 

3.0 23 

2 — 


4^1 

3^ 

IRON SET 

SCREWS 

v 

2 i 

4 

2.176 

3.7/Q 


4s 

5 — 
64 



■ 

-«-L - 

REGULAR S 

—i 

«H ■* 

Q. K 

V 

HEAD 

** 

A 

2.4 26 

4.622 

2 I 

4— 
^32 

6 

4± 

3 


2.629 

5.4 2 8 

3 

5 s 

‘g 

«f 


3 -; 

2.879 

6.509 


*/§ 

7 l 6 

5 

\-ur urv nvjuiNu i 

THREADS U.S. STANDARD 
F-H. SAME AS DIAM.OF 
SCREW. g 

DIAMETERS FROM^ TO 
LENGTH UNDER HEAD 3 L 
VARIES FROM^'tOS" 



3.100 

7.547 

4 



*t 


3 

3.3 / 8 

8.64 / 

3| 

r 2 ' 
^32 



4 

3 

3.567 

9.993 

4 

7 — 

' 32 

8 ti 

6 i 


Plate Q. 






































































70 


MACHINE SCREWS. 1. Standard machine screws are 

shown on Plate R. The values in the table are very close to the 
A. S. M. E. Standard. 

TAPERS. 1. When it is desired that two or more pieces 
shall fit tightly and at the same time be readily removable or 
adjustable for taking up wear, one or more of the pieces are made 
tapering. 

2. The necessary dimensions are those of the larger end, 
the length of the tapered portion and the taper per foot or fraction 
of an inch in a whole number of inches, i. e., in 5". (See Fig. 48.) 



3. On a tapered piece that does not fit anything, give the 
size at each end and its length. The rate of taper must not be 
given. 

4. There is no universal standard for tapers, different lines of 
work and different shops adopt tapers suitable to their require¬ 
ments. The following, used in locomotive practice, is a fair sample: 
Bolt Taper 3 ^" in 12". Boiler Taps 1" in 12". 

Cross-head Pins i" in 5". Brass Cock Plug 2J" in 12". 

Cross-head Key f" in 8 ". Cross-head End of Piston Rod J" in 5". 
Connecting Rod, Stub Keys and Cotters f" in 12". 

























































































71 


STANDARD MACHINE SCREWS 

AMERICAN SCREW COMPANY 


FLAT HEAD 



ROUND HEAD 



Ld 

co 

A 


KF 


FILLISTER HEAD 

C 


D- 


~T~ 

< 


T£ 

to-r 

1 






FH- 



Fh- 


NO 


FLAT HEAD 


ROUND HEAD 


FILLISTER HEAD 


2 

3 

4 

5 

6 

7 

a 

9 
IO 
I 2 
14 
16 
I 8 
20 
22 
24 
26 
28 
30 


.0842 
.0973 
.1)05 
.1236 
.1368 
.1500 
. 163 ) 
.1763 
.1 894 
.2158 
.2421 
.2684 
.2947 
.3210 
.3474 
.3737 
.4000 
.4263 
.4526 


.1631 

.) 894 

.2158 

. 242 ) 

.2684 

.2947 

.3210 

.3474 

.373 7 

•4-263 

.4790 

.5316 

.5842 

.6368 

.6895 

.7421 

.7421 

.7348 

.8474 


.04-54 
.0530 
.0605 
.0681 
.0757 
.0832 
.090 8 
.0984 
.1059 
.1210 
.1362 
,15 13 
. 1665 
,18)6 
,1967 
,21 18 
,1967 
2118 
2270 


.030 

.032 

.034 

.036 

.039 

.041 

.043 

.045 

.048 

.052 

.057 

.06) 

.066 

.070 

.075 

.079 

.084 

.088 

.093 


.OISI 

.0177 

.0202 

.0227 

.0252 

.0277 

.0303 

.0328 

.0353 

.0403 

.0454 

.0504 

.0555 

.0605 

.0656 

.0706 

.0656 

.0706 

. 07 57 


.1544 
.1786 
.2028 
.2270 
.2512 
.2 754 
.2996 
.3238 
.3480 
.3922 
.4364 
.4-806 
.5248 
.5690 
.6106 
.6522 
.6938 
.7354 
.7 770 


.0672 
.0746 
.0820 
.0894 
.0968 
.1042 
.1116 
.1 190 
.1264 
.14 12 
.1560 
.1708 
.1856 
.2004 
.2152 
.2300 
.2448| 
.2596 
.2744 


.030 

.032 

.034 

.036 

.033 

.041 

.043 

.045 

.048 

.052 

.057 

.061 

.066 

.070 

.075 

.079 

.084 

.088 

.093 


.0403 
.04481 
.0492 
.0536 
.0580 
.0625 
.0670 
.0714 
.0 758 
.0847 
.0936 
.1 024 
.1 I 14 
.1202 
.1291 
.1 380 
.1469 
.1 558 
.1646 


.1 350 
.1561 
.1772 
.1984 
.2195 
.2406 
.2617 
.2828 
.3040 
.3462 
.3884 
.4307 
.4729 
.51 52 
.55 74 
.5996 
.6419 
.6841 
.7264 


.054 3 
.0634 
.0720 
,0806 
,0892 
0978 
.1 063 
.1 149 
.1235 
.1407 
.1578 
) 750 
.192 I 
,2093 
.2267 
2436 
2608 
2779 
2951 


.Ol 26 
.0146 
.0166 
.0186 
.0205 
.0225 
.0245 
.0265 
.0285 
.0324 
.0364 
.0403 
.0443 
.0483 
.0520 
.0562 
.0601 
.064) 
.0681 


.030 

.032 

.034 

.036 

.039 

.04) 

.043 

.045 

.048 

.052 

.057 

.061 

.066 

.070 

.075 

.079 

.084 

.088 

.093 


.0338 
.0390 
.04+3 
.0496 
.0549 
.0602 
.0654 
.0707 
.0760 
.0866 
.0971 
.1077 
.1182 
.1288 
.1384 
.1499 
•) 605 
.1710 
.1816 


MACHINE SCREWS ARE DESIGNATED THUS- 12X20 FILLISTER 
HEAD MACHINE SCREWS*' WHICH MEANS SIZE (GAUGE) **12 HAVING 
20 THREADS PER INCH THEREON. SEE LAST COLUMN IN THE 
TABLE OF STANDARDS FOR WIRE GAUGES. 

THE NUMBER OF THREADS PER INCH FOR THE VARIOUS SIZES 
WILL BE FOUND IN THE FOLLOWING TABLE. 


NO 

THREADS 

PER INCH 


NO 


THREADS 

PER INCH 

2 

64 

56 

48 






1 2 

24 

20 







3 

• • 

56 

48 






14 

24 

20 

1 8 

. . 

• • 




4 




40 

36 

32 

• • 

• • 

1 6 

• • 

20 

1 8 

1 6 

# • 




5 




40 

3 6 

32 

• • 

• • 

18 

• • 

20 

18 

1 6 

• • 




& 





36 

32 

30. 

t • 

20 

• • 

- • • 

1 8 

1 6 

• • 




7 






3 2 

30 

• • 

22 

• • 

• • 

1 8 

1 6 

• • 




8 

• • 

• • 

• • 

• , 

36 

32 

30 

• • 

24 


• • 

1 a 

1 6 

14 




9 

• • 

• • 

• • 

• . 

• • 

32 

30 

24 

26 

• • 

• • 

• • 

1 6 

1 + 




1 O 






32 

30 

24 

28 




1 6 

14 













30 

• •: 

* m 


1 6 

14 





Plate R 






















































































72 


STANDARD STEEL TAPER PINS. 1. These pins, made 
by Pratt and Whitney Co., taper i" per foot, and lengths vary by 

Size No. 0 1 2 3 4 5 6 7 8 9 10 

Large Diam. 0.156 0.172 0.193 0.219 0.250 0.289 0.341 0.409 0.492 0.591 0.706 

Length !-l |-li f-1* f-li f-2 f-2* f-3± 1-3* lp| l|-5i 1^-6 

PIPE. 1. Iron pipe is always specified by its nominal 
internal diameter. The pipe table, Plate S, shows that the actual 
sizes differ from the nominal. Use actual sizes on drawings. 

2. A pipe tapped hole is indicated by two circles, the inner 
one being full and equal to the drill size, the outer one half full 
and half dotted and equal to the outside diameter of the pipe. 
(See illustration on Plate S.) 

3. Tubes of iron, steel, brass, copper, etc., are specified by 
their outside diameter and a gauge number for the thickness of 
the material, thus: 2" brass tube, 12 B. & S. gauge. 

STANDARD GAUGES. 1. Standard gauges for Wire, Plate 
Tubes and Screws are given in Plate T. 

WEIGHTS OF CASTINGS AND FORGINGS. 1. The 
approximate weight of a piece is often required, especially for 
making estimates of cost from drawings. This is done by finding 

the volume and multiplying by the specific weight of the material 
of which it is to be made. As results within 10 per cent of actual 
weight are considered satisfactory in practice, it is not necessary 
to consider small fillets and other minute details. 

2. Assume the piece divided into a number of parts, the 

volumes of which are readily obtainable. From these the total 
volume and weight may be found. 

3. If close estimating is required and there are numerous 
fillets of some size, the fillets and round edges should be taken 
into account. See Fig. 49 for the method of finding areas of fillets, 
round edges and corners. 


WEIGHTS OF METALS 

INUM WFIf^l-4«=» 


ALUMINUM 

WEIGHS 

.094 # PER CU. IN 

BRASS 

it 

.30 # i, 

¥ 

BRONZE AND COPPER 

n 

.3 1* „• 

¥ 

CAST IRON 

u 

.26^ - 

¥ 

CAST STEEL 

,i 

.28^ * 

¥ 

LEAD 

- n 


¥ 

WROUGHT IRON AND STEEL. 

•> 

.28* // 

U 


LET A m AREA OF CROSS SECTION OF A FILLET 
A=C-E» C = R z B = 2^?* 

A “ C. — B =* = Ft*- .78S4R 2 = R 2 (l -.7Q54-) 

THEREFORE A=».2.14<oR 2 = .Z ^APPROXIMATELY 



Fig. 49. 



73 


THREAD GO’ 


mm. 


it 


TF-- 
■ | 

1 


|J F — 


i ■ 


¥3 



CONVENTIONAL METHOD TO BE 

USED WHEN D, AFTER BEING 
“ DRAWN TO SCALE, MEASURES 
LESS THAN ONE INCH. 

PIPE THREAD TAPERS I IN 32 TO AXIS. 
^ 0R^"lN DlAM. 

PER FOOT. 

DRAW PIPE 
THREADS 
AS SHOWN. 

ACTUALLY _ 

THE THD5. 

FURTHEST 
FROM END 
ARE NOT 
PERFECT, 

SEE TABLE. 


/ 

/ / O 

1 

~^X\ 

1 \ 

[{A 

\Jd 

\_ 

\ 

J- PIPE TAP 
4 • 

L.H THD ' 


WROUGHT IRON STEAM, GAS AND WATER PIPE 

NATIONAL TUBE COMPANY — STANDARD DIMENSIONS 


DIAMETERS 

TRANSNy 

INTER 

ARE 

'ERSE 

INAL 

AS 

THREADS 

DRILL 

HOLE 

FOR 

TAP 


ACTUAL 

NOMINAL 

INTERNAL 

INTERNAL- 

EXTER 

NAL 


NO 

PER 

INCH 

LENGTH 

THREADED 

LENGTH 

PERFECT 

AT ROOT 

STAN 

DARD 

EXTRA 

HEAVY 

STAN 

DARD 

EXTRA 

HEAVY 

'/a 

270 

.205 

.405 

.057 

.0 3 3 

27 

& 

3 /* 

% 

A 

.3 64 

294 

.54 0 

.1 04 

.068 

1 8 

% 


% 

3 /e 

.4 34 

.42 1 

.675 

.19 1 

.1 39 

18 

& 

T, 

% 

h 

.62 3 

.542 

.84 0 

-304 

.231 

14 

’-4 

% 

% 

% 

.824 

.736 

1.050 

.53 3 

.425 

14 


% 

% 

1 

1.048 

.95 1 

1.3 1 5 

86 1 

.7 / 0 

1 l'/2 

% 

‘4 

1% 


/.380 

1.2 72 

1.660 

1.496 

1.27 1 

1 i '/ 2 

"4 


i% 

\V L 

1 .6/ / 

1.4 94 

1.900 

2.036 

1.753 

' 1 *4 

% 

%. 

i% 

2 

2.0 fc 7 

i. 9 33 

2.375 

3.356 

2.9 3 5 

h‘/ 2 

7 /8 

TU 

z\ 


2.4 6 8 

2.3 1 5 

2.875 

4.7 80 

4.2 09 

8 

* 1 

7 /8 

2%. 

3 

3.0 6 7 

2.892 

3.500 

7.383 

6.569 

6 

1 

% 

3% 

3k 

3.54 8 

3.358 

4.000 

9.8 87 

8.056 

8 

1 '//(, 

1 

5% 

c 

4 

4.0 2 6 

3.81 8 

4.500 

1 2.730 

1 1.449 

8 

»'/a 

l%4 

4% 

4k 

4.5 0 8 

4.2 80 

5.000 

1 5.961 

1 4.387 

8 

>'4 

*&4 

4% 

5 

5.045 

4.81 3 

5.5*6 3 

1 9.905 

1 8.1 93 

8 


l%2 

5 % 

6 

6.0 6 5 

5.7 5/ 

6.6 2 5 

2 8.88 6 

2 5.976 

8 


*4 


7 

7.0 2 3 

6.625 

7.6 25 

3 8.743 

3 4.47 2 

8 

«’4 

l 5 /a 

l7/U 

8 

7.98 2 

7.625 

8.6 25 

5 0.0 2 1 

45.664 

8 



8% 

3 

8.9 3 7 

8.62 5 

9.6 2 5 

62.722 

5 8.4 2 6 

8 


1%, 

*7a 

to 

/ 0.0 1 -9 

9.7 50 

! OJ SO 

78.822 

74.662 

8 


Ah 

10% 


1 l nnrt 


1 1.750 

9 5.034 


8 


i% 

i i7/6 

1 i 

1 2 

1 2.000 

1 L750 

IZJ50 

113.090 

108.43 0 

8 

i* 

i% 

\Z 7 /lb 


Plate S, 

































































































74 


STANDARDS FOFLWIRE GAUGES 

IN USE IN THE UNITED STATES 

DIMENSIONS ARE IN DECIMAL PARTS OF AN INCH 

i 

MACHINE AND WOOD 

SCREW GAUGE 

NUMBER OF 

WIRE GAUGE 

AMERICAN 

OR BROWN 

AND SHARPE 

BIRMINGHAM 

OR STUBS 

ENGLISH 

STUBS 

STEEL WIRE 

U. S, STANDARD 

FOR PLATE 

NUMBER OF 

SCREW OR WIRE 

GAUGE 

000000 




.4688 

OOOCOO 


00000 




.4375 

00000 


OOOO 

.46 

.4 54- 


.4063 

OOOO 

. 

OOO 

.409 6 

.425 


. 3 750 

OOO 

.03 1 5 

00 

.3648 

.38 


.3438 

OO 

.0447 

0 

. 3249 

.34 


.3 125 

O 

.0578 

1 

.2 893 

. 3 

.227 

.281 3 

1 

.07 10 

2 

.2576 

.2 84 

.2 1 9 

.2 656 

2 

.0 842 

3 

.2 294 

.259 

.2 1 2 

.25 

3 

.0973 

4 

. 2043 

.238 

.207 

.2344 

4 

.1105 

5 

.16 19 

.22 

.2 04 

.2188 

5 

.1236 

6 

.1620 

.203 

.20 1 

.203 1 

6 

.1368 

7 

.1443 

.1 8 

.1 99 

. 1 875 

7 

. 1 500 

8 

.1285 

.1 65 

.197 

.17/9 

8 

.1631 

9 

.1 144 

.148 

.1 94 

.15 6 3 

9 

.1763 

10 

.10 19 

.1 34 

1 9 1 

.1406 

IO 

. 1 894 >■ 

1 1 

.0907 

.1 2 

.188 

. 1 25 

1 1 

.2026 

12 

.0808 

./ 09 

.1 85 

.1 094 

1 2 

.2 1 58 

13 

.07 20 

.095 

.1 82 

.0938 

1 3 

.2289 

14 

.064 1 

.083 

.180 

.0781 

14 

.242 1 

15 

.057 1 

.072 

.1 78 

.070 3 

1 5 

.2 552 

16 

.0508 

.065 

.1 75 

.0625 

1 6 

.2 684 

1 7 

.0453 

.05 8 

.1 72 

.0563 

17 

.28 1 6 

1 8 

.0403 

.049 

./ 68 

.05 

1 8 

.2947 

19 

.0 359 

.04 2 

.1 64 

.0438 

19 

.3079 

20 

.03 2 O 

.035 

.1 6 1 

.0375 

20 

.3210 

2 1 

.0285 

.032 

.1 57 

.0 344 

2 1 

.3342 

22 

.0253 

.028 

.1 55 

.031 3 

22 

.3474 

23 

.02 26 

.025 

.1 53 

.0281 

2 3 

.3605 

24 

.020 1 

.022 

.151 

.025 

24 

.3737 

25 

.O \ 79 

.02 

.148 

.02/9 

25 

.3868 

26 

.Ol 59 

.0 18 

.1 46 

.Ol 88 

26 

.4000, 

2 7 

.O 142 

.O | 6 

.14 3 

.0/72 

27 

.4132 

20 

.O 1 26 

.0 14 

.1 39 

.0/56 

28 

.4263 

29 

.Ol 13 

.0 13 

.13 4 

.0 140 

29 

.4 395 

30 

.OIOO 

.0 1 2 

.12 7 

.0/25 

30 

.4526 

3 1 

.0089 

.O 1 

.120 

.0/ 09 

3 1 

.4658 

3 2 

.0080 

.009 

.1 1 5 

.O / 02 

32 

.4790 

33 

.007 / 

.008 

.1 1 2 

.0094 

33 

,43a i 

34 

.0063 

.007 

.1 1 o 

.0086 

34 

.505 3 

35 

.0056 

.0 05 

.1 OS 

.0078 

35 

.51 84 

36 

.005 

.004 

.1 06 

.0070 

36 

.53 1 6 

37 

.0045 


.1 03 

.0066 

37 

.5448 

38 

.0040 


.1 Ol 

.0 063 

38 

.5579 

39 

.0035 


.0 9 9 


39 

.5711 

40 

.003 1 


.097 


40 

.5842' 


Plate T, 






























75 


DECIMALS OF AN INCH FOR EACH 64 

th 

32nds 

64ths. 

DECIMAL 

FRACTION 

32 nos. 

64ths. 

DECIMAL 

FRACTION 


1 

.015625 



33 

515625 


1 

2 

.03125 


17 

34 

.53125 



3 

.046875 



35 

.546875 


2 

4 

.0625 

1-16 

18 

36 

.5625 

9-16 


5 

.07812 5 



37 

.573125 


3 

6 

.09375 


19 

38 

.59375 



7 

.109375 



39 

.609375 


4 

8 

.125 

1-8 

20 

40 

.625 

5-8 


9 

.140625 



41 

.640625 


5 

10 

.15625 


21 

42 

.65625 



1 1 

.171875 



43 

.671875 


6 

12 

.1875 

3-16 

22 

44 

.6875 

11-16 


13 

.203125 



45 

.703125 


7 

14 

.2 1 875 


23 

46 

.71875 



IS 

.234375 



47 

.734375 


8 

16 

.25 

1 -4 

24 

48 

.75 

3-4 


17 

.265625 



49 

.765625 


9 

18 

.28125 


25 

50 

.73125 



19 

.296875 



51 

.796375 


IO 

20 

.3125 

5-16 

26 

52 

.6125 

13-16 


2 1 

.328125 



S3 

.828125 


1 1 

22 

.34375 


27 

54 

.84375 



23 

.359375 



55 

.859375 


12 

24 

.375 

3-8 

28 

56 

.875 

7-8 


25 

.390625 



57 

.890625 


13 

26 

.4062 5 


29 

58 

.90625 


27 

.42/875 



59 

.92/875 

15-16 

14 

28 

.4375 

7-16 

30 

60 

.9375 


29 

.453125 



6 1 

.953125 


15 

30 

.46875 


3 1 

62 

.96675 


3 1 

.484375 



63 

.984375 


16 

3 2 

.5 

1-2 

3 2 

64 

1 . 

1 


Plate U. 












76 



GEOMETR 
TO INSCRIBE A PENTAGON 
IN A GIVEN CIRCLE. 

. Bisect the rad/i/s atR 
b With /fas a center 
anct rad/'us fiO c/raw 
&re Oh 77?e core? OR 
w///step off 5 times. 


TO bRAWA CIRCULAR ARC 

THROUGH 3 POINTS A,Bf. 

W/fh fcztAandC 
* atawares C6 & A K. 
Dnaw/1 3 to 3 and 
CBtoG. Di\/icteC3 
•i %A&/h/o £y zVo.par- 
ts conAhi/e to 


C DRAWING 

TO CONSTRUCT ANY POLYGON 



ON A GIVEN LINE-CO. 
Draw arc with CD 
as mafius. ctiv/c/e // 
/nto sa/ne A/o. /parts 
as potyyon has s/ctes 
fro/?? 2~ y /oo/f7t;2E*CD. 



TO CONSTRUCT A PARABOLA 
+ 3 Z ! o I 234 Spa /7 $ Rise y/yen. 

d Divide the rise ^4d 
\ cyt/a/parts 

^anaZCRt/hto sa/??e 
\v Cna/nher Jo//? c/S 
jf \d c.cf with O /nfer- 

fsect/hy vert/ca/s art /oo/nfs fte<?k 




TO DRAW AN ACCURATE ELLIPSE 
BOTH AXES GIVEN 

Draw c/rc/es w/th 
/ney'orax/sA/Af & 
p* n/z/rarax/sAZ/vas 
Dzd/ns. Drawnxtld 
Jhes Avy/po/af/o z 
^ '/sat \f&/tZ$v//ro/n2&Z, 

TO DR AW A SPIRAL lay O/t' The 

* racf/Os Vec/orfO 
//? cty/fere/?/ 
g /oos/f/cHvsat 
eyc/a/any/?s 
' \ aacXcX/r/a'te/Y 
| I /s?/o eyaat 
ITS part? o/ 23 



TO DRAW AN INVOLUTE 

5 * 3 2 1 ^ Draw 06 Ta^ 



foD/am.Oa 


~to sen?/c/r 


'Ct/zn/erence, 
Ata/re OAercOi 

y/ 7 dn. fo C/etc, 

epicycloid 

DWde ro////y 
f* c/re/e//r- 
fo eyua/ 
yaar/sew’ 
_Xjc \**a4v/wk' 
yeyre/et/rt; 
P^oa^orcoi 


T6 LAY OFF AN ARC EQUAL TO 

A1 - |E , ■ .B LENGTH or STRAIGHT 

line Divide/zhe A8 
z/7to 4eyoa//earts t 
frozn J M /oo/ht£ 
c/raw arc 3D. 
Length 40 of&rc 

yyat/eny//? ofy/i/en/sreJB. 



TO COKISTRUCTA HYBERBOLA 

: Give/? transverse, 

* axis vt 3 and/oc/yf 
7a/re any/po/nts 
p T i ZJ. 4 on ax/s £3 
A/a/re fa=A/ave//a=Bl' 
Afa/reJe =££ =/4Z. 
fVot sv/^/czent/ao/Rfs 



TO DRAW APPROXIMATE ELLIPSE 

J- 


-Q oa'rDD 
1reo/.*a& 07^/vfAf 


to 'Draw a +center spiral 

Consfre/cfasyoazt 
/23ft with su/77 of 
siJes eac/a/fhe 
/o/tch t-C an ct 
/oro/ony sides in 
one ortnect/on. 
WZth <y 2 a/raw arc//? arcah 



TO DRAW A cycloid, (jn rase 

< y/aen?o'*e Oa=a/?^ arcs o/ t Z2 



>5. ro/t/hyc/rc/e/nto 
i\/z/ '' x e<?csa/ / t?arfs 0{/Z t 
K 23etc and/nafre 
the hose cvirc/e 
, arcs Oa; ah 
/at arcs 
’ etc. 


Plate V. 





































































11 


CHECKING. 1. A Mechanical Drawing is always checked 
for errors, omissions and correctness in representation before it 
reaches the artisan. 

2. The designer and draftsman should each check their work 

for their own satisfaction and protection. This should be done as 
the work progresses. 

3. A drawing should be checked by some one familiar with 
the requirements other than the draftsman that made it, to avoid 
costly mistakes, doubtful meaning and impractical construction. 

4. Drawings are corrected to make them right and explicit. 

5. Erasing and making corrections on a drawing is easier and 
cheaper than making alterations on a piece in the shops— it keeps 
things from going to the scrap pile. 

Check mark- o./f. 

Dra w a center line 
Erase the l/ne 
Draw a sol/d l/ne 
Dot the l/ne 

Shade l/ne - Wo shade l/ne 
E/cl/res,a1rro\a/s etc oh/ tted 
D/mens/on /s /ncorrec t 
Take out— Useless 
Meaw/wo /s not clear 
F/ y- (5 /\ae th/s attention 

Fig. 50. 

6. Check a drawing for the following features and make the 
required changes. (See Checker’s Symbols, Fig. 50.) 

Clearness.— Is the drawing easy to read and understand? 

Are the lines correct in weight and punctuation? 

Views.— Are they correctly projected from each other? 

Do they show the object completely ? 

Would others show the object to better advantage? 

Sections.— Are they drawn correctly and their locations indicated? 

Are others needed to show the construction? 

Dimensions. —Are the values correct by scale or calculations? 

Are enough given for complete information and no repetitions ? 
Are necessary ones given without resort to addition and sub¬ 
traction ? 

Are they the ones wanted and properly placed for usefulness? 


/ 


l l llll HlllllDIIUK - 

S — A/6 - 


■po77 











78 


Lettering.—Are all symbols for Finish, Fit and Identification given? 

Has all material been correctly specified ? 

Have all parts been tabulated in the Bill of Materials? 

Are all necessary notes given? 

Does the title contain the necessary and correct information? 

Is the index number, for filing and identification correct ? 
Design.—Is the design practical and of pleasing appearance? 

See Practical Points in Mechanical Design Drawing, Page 79. 
Motions.—Do moving parts have proper clearance? 

Fastenings.—Can they be readily put in place and removed? 

DESIGNING. 1 . A mechanical scheme may originate in the 
mind without a demand for it, or the idea may have to be evolved 
by the pressure of necessity; in the latter case considerable design¬ 
ing is required. 

2. A design is developed by analytical and empirical methods 
augmented by the designer’s mechanical sense of proportions. 

3. Analytical design involves the determination of dimensions 
by mathematical formulas, deducted from scientific theories and 
tests which the designer should understand. 

4. Empirical design is determining size by formulas and pro¬ 
portions based on experience, observation and good practice. 

5. Mechanical sense of proportion is that ability which enables 
one to design the thing required, using previously determined sizes 
or quantities to build around. 

6. The procedure in Mechanical Design should be about as 
indicated in the following typical schedule: 


1. 

2 . 

3. 

4. 

5. 

6 . 

7. 

8 . 
9. 

10. 


TYPICAL DESIGN SCHEDULE 
Main Features 

The thing required. 

Specifications to be met. 

General scheme of layout—scheme sketches. 

Analysis and calculations involving forces, 
velocities, friction, etc. 

Memorandum sketches for dimensions and 
quantities calculated. 

Empirical proportioning of parts. 

Standard proportions of parts. 

Mechanical sense of proportions. 

Layout of main center lines, base lines, clear¬ 
ance and reference lines. 

Drawing the design accurately and in logical 
order. 


Order of Procedure 

Subject 

Given 

Required 

Scheme 

Mechanism 

Assumptions 

Analysis 

Procedure 

Formulate 

Calculate 

Result 

Deductions 

Conclusions 

Drawing 




79 


7. Mechanical design drawing requires a full knowledge of 

Mechanical Drawing, the Theory of Design and Shop Methods of 

Construction. 

8. Practical points to observe in designing: 

Keep notes, in loose-leaf form, in a neat and logical order, including 
all sketches, calculations and memoranda. 

Be systematic in designing and drawing; it is the shortest and 
best way to get results. 

Freehand sketches make good memoranda as the work progresses. 

Views showing sections make a drawing clear and more workable. 

Cost of construction and ease of operation are controlled by the 
designer. 

Take no risks in proportioning parts where their safe size can be 
calculated. 

Make reasonable assumptions and test their fitness by calculation 
or graphical trial. 

Think of the construction, fabricating and machining of the parts as 
the drawing progresses—impractical and impossible design 
must be avoided. 

The general appearance should be harmonious in design, not ugly. 

Things that are right look right —is true. 

Erecting must be done with the least effort. 

Dismantling for cleaning or replacements should be the least possible. 

Take a machine apart mentally while drawing it. 

Adjustment for wear must be provided and accessible for take-up. 

Adjustment for centering should be provided when necessary. 

Centering and lining up must be provided for by pins or projections 
in recesses. 

Parts should be few in number, especially those to be replaced. 

Moving parts must not foul anything; leave plenty of clearance. 

Right and left-hand parts should be avoided; they are not inter¬ 
changeable. 

Minor details omitted cause delay, inconvenience and expense. 

Non-essentials should be omitted from the design—aim for 
simplicity. 

Thin ribs will crack if adjoining wall is quite thick. 

Fillets must be shown; sharp corners are weak and undesirable. 

Round edges must be shown where required. 

Oil holes and grooves must be provided and be easy to reach. 

Standard fastenings, fittings and parts should be used to reduce 
costs. 

Through bolts are preferred to studs and studs to cap bolts. 


80 


Bolts should have room for inserting and forced removal. 

Nuts and cap bolts must be free to turn when near fillets, ribs or 
walls. 

Check nuts or cotter pins should be specified where needed. 

Machine screws are preferable to bolts on small work. 

Set screws should be used for holding parts in place, not for trans¬ 
mitting any considerable force. 

Keys are fastenings used to transmit appreciable force. 

Keys should have room for inserting and be easy to remove. 

Tapering cotters are fastenings used where adjustment and quick 
release are required. 


INDEX 


PAGE 


Abbreviations—Fig. 20. 23 

Arrangement of Views—Fig. 10, Fig. 

11. 13 

Arrow Heads—Fig. 18, Fig. 19. 20 

Assembly Drawings. 57 

Bill of Materials—Plates H,J. 51 

Blue-prints. 58 

Bolts—Plates P, Q. 65 

Checking—Fig. 50. 77 

Classification of Drawings. 4 

Conventional Threads—Fig. 46. 64 

Cored Holes—Fig. 47. 65 

Cross-hatching—Plate A, Fig. 24. 25 

Decimal Equivalents—Plate U. 75 

Designing. 78 

Developments—Fig. 29. 39 

Dimensioning—Fig. 18, Fig. 19.20 

Erecting Drawings. 57 

Essentials. 4 

Figures—Fig. 18. 20 

Finish Marks—Fig. 21. 23 

Finished Surfaces. 24 

Fitting Symbols—Fig. 22. 24 

Fractions—Fig. 18. 21 

Gears—Plates L, M. 58 

Geometric Drawing—Plate V. 76 

Inking In. 19 

Instruments—Fig. 1, Fig. 2. 5 

Intersections—Fig. 26, Fig. 27, Fig. 28 35 
Laying out Views—Fig. 12. 14 


Isometric Drawing—Figs. 30, 31, 32, 

33, 34, 35, 36, 37. 40 

Lettering, Fig. 40, Fig. 41, Plates E, F 49 


Line Shading—Fig. 25, Plates B, C, D 31 

Lines—Fig. 13, Fig. 14, Fig. 15. 15 

Machine Screws—Pl^te R. 70 

Number Circle—Fig. 4, Fig. 5. 7 

Omitted Dimensions. 22 

Pipes and Tubes—Plate S. 72 

Preface. 3 

Projection—Fig. 9. 10 

Scales. 13 

Screw Threads—Fig. 42, Fig. 43, 

Fig. 44. 61 

Screw Threads. Proportions and 

Tables—Plates N. O. 65 

Sections—Fig. 16, Fig. 23. 24 

Shade Lines—Fig. 17. 19 

Size of Sheets—Fig. 6, Fig. 7, Fig. 8. 8 

Size of Tracings—Fig. 8. 8 

Sketching—Fig. 38, Fig. 39. 44 

Standard Wire Gauges—Plate T. 72 

Sub-Captions—Plate H,I. 51 

Tabulated Dimensions—Plate 1. 22 

Tapers—Fig. 48. 70 

Taper Pins, Standard. 72 

Tapped Holes—Fig. 45. 63 

Tinting. 28 

Titles—Plates G, H,J,K. 51 

Tracings. 57 

Trimming Drawings. 10 

Use of Instruments—Fig. 3. 6 

Weights of Castings and Forgings— 

Fig. 49. 72 

Wire and Screw Gauges—Plate T. . .. 74 


( 81 ) 

























































LIST OF ILLUSTRATIONS 


FIGURE PAGE 

1— Instruments in Case. 5 

2— Irregular Curve.. 6 

3— Use of Triangles. 6 

4— Number Circle. 7 

5— Part Number Circle. 7 

6— Size of Sheets, Form 1. 8 

7— Size of Sheets, Forms 2 and 3.. .. 9 

8— Size of Sheets, Form 4. 9 

9— Projection Planes. 11 

10— Object Surrounded by Planes. 12 

11— Position of Views. 12 

12— Laying out views. 14 

13— Lines (Samples of). 15 

14— Dotted Lines. (Ending). 15 

15— Piston (Contrast of Lines). 16 

16— Coupling (Use of Lines). 17 

17— Shaded Lines. 18 

18— Size of Figures and Arrows. 20 

19— Dimensioning Small Spaces. 21 

20— Abbreviations and Symbols. 23 

21— Finish Marks. 23 

22— Fitting Symbols. 24 

2 3—Section Planes. 25 

24— Breaks in Long Pieces. 27 

25— Line Shading (Theory).. 30 

26— Intersection of Cylinders. 35 

27— Intersection of Elbow and Cyl¬ 

inder. 36 

28— Intersection of Bell Shaped Sur¬ 

face and Plane. 38 

29— Development of Surfaces. 39 

30— Isometric Projection (Theory)... 40 

31— Isometric Projection (Theory).. 40 

32— Isometric Projection (Theory).. 41 

33— Isometric Axes and Planes .. 41 

34— Isometric Projection of Circles... 42 

35— Isometric Plotting. 43 

36— Isometric Projection of a Circle. . 43 

37— Isometric Drawing. 43 

38— Sketch. 45 

39— Sketch (Details). 47 


FIGURE PAGE 

40— Block Letters. 49 

41— Ruled Letters. 49 

42— Screw Thread. (Helix). 61 

43— Screw Threads. (R & L, V 

&Sq.).. ... 62 

44— Section Through Threads. 63 

45— Tapped Hole. 63 

46— Conventional Threads. 64 

47— Holes (Cored and Bored). 65 

48— Tapers. 70 

49— Weights of Metals. 72 

50— Checkers’Symbols. 77 


PLATE 

A—Conventional Standard Cross¬ 
hatchings. 26 

B—Line Shading. (Examples). 32 

C—Line Shading. “ . 33 

D—Line Shading. “ . 34 

E—Freehand Letters. 48 

F—Lettering. (Heights). 50 

G—Titles. (General). 52 

H—Titles, Sub-Captions, Bill of 

Materials. 53 

I—Tabulated Dimensions. 54 

J—Titles. (Manufacturers). 55 

K—Titles. (Design). 56 

L—Drawing the Involute Tooth. 59 

M—Drawing Bevel Gears. 60 

N—U. S. & V. Standard Threads. 

(Proportions). 66 

O—Square and Acme Standard 

Threads (Proportions). 67 

P—Bolt Heads and Nuts. 68 

Q—U. S. Screw Threads and Nuts. .. 69 

R—Machine Screw. 71 

S—Pipe Threads, Table of Sizes. 73 

T—Wire and Screw Gauges. 74 

U—Decimal Equivalents. 75 

V—Geometric Drawing. 76 


( 82 ) 



































































CHECKING INDEX 


WITH REFERENCES FOR CORRECTING DRAWINGS. 


TOPIC 


PARA. PAGE TOPIC 


PARA. PAGE 


ABBREVIATIONS ERASING 

Conventional.Fig. 20 - 23 Paper rough, restore. 5-20 


BILL OF MATERIAL FINISH MARKS.Fig. 21 F.M. - 23 

Form used.Plate H. Bot. 1-51 FITTING SYMBOLS.F.S. - 24 


BOLT HEADS & NUTS 

Sizes.1 & 3 - 65 

CHECKING & CORRECTING 

Own work for protection. 2-77 

Symbols used.Fig. 50 - 77 

Erase and correct, purpose. .4 & 5 - 77 

Features to be checked. 6-77 

CLEAN PAPER.Top 6-20 

CORES, COUNTER-BORES 

Indicating. 1-65 

CROSS-HATCHING 

Omit at dimension. 1-25 

Same piece, same direction. . . 2-25 

Different pieces, opp. direction 3-25 

Uniform spacing. 4-27 

Black -fa" apart. 5-27 

Bolts, shafts not hatched. 7-27 

Ribs, webs not hatched. 8-27 

Long piece, foreshorten.9 & 10-28 

DEVELOPMENTS 

Line of intersection, determine 1-39 


DIMENSIONS 

Keep in line. 1-20 

Arrow hds. sharp, touch line.. 1 & 2 - 20 

Figures high. 3-20 

Figs, with letters cap. high- 4-20 

Figures off line in open. 5-20 

Crowded, use leader. 7 — 21 

Fractions, size, clear, form- 8-21 

Outside of views, clearness_ 10-20 

Read bottom and right. 12-20 

Necessary, no repetition. 14-20 

Give from CL or “f” surface.. 14-22 
Holes circ. view, & CL. to CL. 15-22 

Full lines to full lines. 16-22 

Useless, impractical. 17-22 

Distribute among views. 19-22 

Arcs, give radii. 20-22 

Circle, give diameters. 21-22 

Omitted,,,.. 23-22 


( 84 ) 


GAUGES, standard.Plate T - 74 

GEOMETRIC DRAWING 

Ellipse approximate by pro¬ 
jection.- 75 

INKING IN 

Lines, thicknes.Bot. 1-19 

Circles and Arcs first. 3-20 

Lines must be black. 4-20 

Letters must be black. 4-20 

Figures must be black. 4-20 

Ragged lines, erasures. 5-20 

INTERSECTIONS 

Plot correctly. 1-35 

Plot sufficient points. 3 & 4 - 36 

ISOMETRIC 

Non-Isometric lines, plot. 5-41 

Circle, plot and draw. 8-42 

Ellipse construction. 9-43 

Center of solid.Fig. 37-43 

LAYING OUT VIEWS 

Distance between. 1-14 

Center and base lines accu¬ 
rately. 3- 14 

Accuracy in laying out. 4-15 

Base face bottom or right.... 6-15 

LETTERS 

Bold strokes. 2-49 

Sizes (titles, notes, etc.). 3-49 

Read lower and right edge_ 6-49 

LINES 


Clear, distinct sharp penciling 1-15 
Dotted, short dashs and spaces 3-15 


Dotted, stagger adjacent. 4-16 

Center, close up breaks. 6 - 16 

Center, bieak in open spaces.. 6-16 

Construction, dash, little space 9-18 


Extension ? cle^r of yiew...... 11 - 18 


















































85 


topic para, page 

NUMBER CIRCLE 

Size and location. 1 - 7 

Part Number. 5- 7 

Index Number. 7 - 8 

PENCIL POINTS 

Sharp point on all leads. 4 - 7 

All leads 6H. 1-15 

PIPE 

Dimensions necessary. 1-72 

Tap, indicating. 2-72 

PROJECTION 

Third angle to be used. 9-11 

SCALES 

Standard scales only used.... 3-13 

Size and scale confused. 5-13 

SECTIONS 

Planes to be lettered. 2-24 

Limit, full line at center. 4-25 

Beyond center, show broken 
line. 5-25 

SHADE LINES 

Thickness, conventional use. . 1-19 

Outside of figure. 2 - 19 

Common, not shaded. 3 - 19 

Determine shade lines. 4 - 19 

Uniform thickness equal to arc 5-19 
Circles, arcs, move needle.... 6-19 

Arc (uniform), joining. 7—19 

Pencil work not shaded. 8 - 19 

Tracings, not generally shaded 9-19 
SIZE OF SHEET 

Form 1-E.Top 2 - 8 

Tracings after correcting.. Bot. 2- 8 

SKETCH 

Title and information.3 & 4 - 44 

Size to draw, clearness essential 5-44 

One part on a sheet.6 & 9 - 44 

Page sheets. 11-44 

Dimensions, show distinctly. . 8-44 

Dimension to “f” surfaces 

and C.L. 17-46 

Holes locate from C.L. 19-46 


TOPIC PARA. PAGE 

SUB-CAPTIONS 

Placing.Mid. 1 & 2 - 51 

TAPERS 

Dimensions necessary.2 & 3 - 70 

TAPS 

Diameter, to determine. 1-63 

Drill size for tapping. 2-63 

Bottom of hole, depth and 

shape. 2-63 

Section through. 3-63 

Indicating by circles and note. 4-64 

THREADS 

Laying out, procedure. 3-61 

Right hand. 4-61 

Left hand. 4-61 

Standard. 7-61 

Single and double distinction 8 & 9 - 62 

Diameter outside. 11-63 

Section through. 12-63 

Hidden, to indicate. 13-63 

THREADS, CONVENTIONAL 

When used. 1-64 

Spacing. 3-65 

When not used. 4-65 

TITLES 

Leave space for it. 7-13 

General form. 1-51 

Detail form. 2-51 

Location. 4-51 

Part numbers required. 3-51 

TRACINGS 

Dull side used. 3-57 

Heavy black lines required_ 4-57 

Not shaded, all lines heavy. . . 5-57 

Lettering, rule guide lines. ... 6-57 

Trim after correcting. 10-58 


TRIMMING 

Completed work to size. 3 - 8 

Tracings full.Top 2-10 

Careless and holes.Top 3-10 


USE OF INSTRUMENTS 

Pencil points.Top 4- 7 

WEIGHTS, estimating.1&2 - 72 



















































































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